You've got a great idea. It's this kid, so your target audience can identify with the main character, traveling around the world, finding Plot Coupons and saving the world. Just one problem: How many days of school has the hero missed? Not everybody can fit adventures into a summer vacation like in Ben 10 and Phineas and Ferb; you want the adventure to last through times that school is usually in session. But this can be solved by simply never, evermentioning it! Fan Wank will take care of the excuses for you!
This is justified if the character is in their late teens, as in many places, finishing high school is not compulsory.
A common trope in adventuring anime, and practically any video game or show that takes place in a world of adventurers (may be justified in the latter if there are no public schools).
The childhood equivalent of One-Hour Work Week.
Sub-trope of The Pirates Who Don't Do Anything. (Think of it as The Students Who Don't Go to School.) Wake Up, Go to School, Save the World averts this.
Yu-Gi-Oh! (in the manga, at least): The two major Yu-Gi-Oh: Duelist arcs take place during school breaks specifically so Yugi can attend, and other arcs take place in only a short time, or after/during school. Yu-Gi-Oh! The Abridged Series parodied the anime version with Joey wondering why they turn up at all, and with Yugi expressing surprise when seeing an actual teacher, having apparently forgotten what they looked like. Even Tristan wonders why they haven't been expelled by now.
Trainers leave for one year, in the The Electric Tale of Pikachu manga series. A rare and little known novelization released early in the anime's life hand-waves this. After children in the Pokémon world finish schooling at the age of ten, they become legal adults who are free to leave to become full-time trainers, or do whatever else they want.
Averted in the Tenchi Muyo! OVA where much of Tenchi's school is destroyed in the first episode and in the second his house is accidentally relocated next to his grandfather's shrine deep in the mountains. He ends up taking his classes by correspondence after that.
In Bleach, the teenage protagonists time their world-saving to take place during school breaks whenever possible, but they still frequently have to cut class to respond to attacks and sometimes get in serious trouble for doing so. Ichigo can at least send Kon in his place but Uryuu, Chad, and Orihime can't fake their absences and come up with often-outlandish excuses. They avert more serious consequences by keeping their grades up so the teachers only have so much to complain about.
In Sailor Moon, the monsters conveniently attack within walking distance (or a short ride via public transportation) from where the main characters live, and unless their plan has something to do with an extracurricular activity, never while the Sailor Senshi are supposed to be at school. This does make some sense, though, since in all but one story arc the protagonists are intimately connected to the Big Bad or have what the Big Bad wants. Also, generally, when the above doesn't apply, the problems are implied to have been happening for some time, and the heroines simply investigate at a convenient, non-school time. Or, the event is actually triggered by the senshi being there. Or, the villain crashes the school and forcibly ends classes, so it's not much of an issue.
In InuYasha Kagome has her family make up a series of unlikely illnesses for her to be suffering from, so that she can spend her time in feudal Japan. Few people seem to question this state of affairs. In a What an Idiot example at one point in the manga, one of Kagome's schoolmates sees her come out of the Bone Eater's Well just as her grandfather was covering up for her. Still he goes up to her casually and asks her if she's feeling better from her disease.
In Mai-HiME, while most of the HiMEs go to the Academy if they're not employed there, Natsuki is on the rolls but rarely attends class. Nobody makes an issue of it, since it's a School For Scheming and Natsuki's involved in chasing down her past, but in the end, when Natsuki wants to go Walking the Earth on a Journey To Find Herself, she is told quite firmly that she needs to make up all the schooling she's missed. Also, near the end, about half the students (including Student Council President Shizuru) stop attending at all, because the school's half-destroyed, the Masquerade has completely collapsed and there's essentially a war going on; around that point, the school closes and those not involved in the conflict go home.
In A Certain Scientific Railgun most of the characters are in school and some in boarding school but the only time we see anyone in class is during the school holidays. The sister series A Certain Magical Index shows main hero Touma occasionally getting in trouble for missing so many days of school while he's off adventuring, and there are a number of scenes of him in class or participating in school activities. Accelerator is mentioned to be "enrolled" in a school but this is mostly a cover for his activities in Academy City's "dark side". Some other school-aged characters simply ignore school because they're too busy working (usually, again, for Academy City's "dark side"), and Index doesn't go because she entered the city illegally and has no money to pay for it regardless.
Subverted in Soul Eater, where traveling around the world and defeating monsters is their schoolwork.
Dragon Ball: Videl is shown departing high school in the middle of classes to help the police with various criminals pretty often. Interestingly, this is sanctioned: the school apparently counts it as "community service" and she's a good enough student that it doesn't affect her grades. Played for Laughs with Gohan, who always uses the excuse that he has to go to the bathroom. This is eventually lampshaded by one of his teachers, who points out that he often doesn't return to class and refuses to give him permission (he taps his foot in annoyance and inadvertently causes an earthquake, allowing him to leave school anyway).
Though the heroes of Dinosaur King do attend school in a couple of episodes, somehow the Dinosaurs of the Week never appear during school hours, and on the two cases of the heroes being in school, they're on a field trip.
Mariko on Bodacious Space Pirates is explicitly shown to be attending school while captaining the Bentenmaru, although her grades are suffering.
Suske en Wiske: School is never mentioned. They always have spare time to go on adventure.
Jo Zette And Jocko: Not implied in this comic strip either. Jo and Zette have adventures, but are never seen going to school.
Animorphs: The team goes to great lengths to make missions possible or delay them when they coincide with school hours, eventually asking the Chee to impersonate them when necessary.
Akiko on the Planet Smoo has a robotic doppelganger take her place over the course of the adventure, since she's gone in real-time.
Skulduggery Pleasant has Stephanie/Valkyrie's reflection replace her in school whenever she's learning magic/saving the world.
In The Dangerous Days of Daniel X by James Patterson, it is handwaved by saying that Daniel is so smart he does not need to go to school. He avoids truancy officers by using his powers to create his mom and dad, who say that he's homeschooled.
Averted in the Alex Rider series. The second book opens with Alex complaining about all the make up work he has to do for the weeks of school he missed in the first book. And later in the series, after he realizes how much saving the world every few months sucks, he starts saying "Why can't I just be in school?" Naturally, every attempt to back out of his spy life just throws him in even deeper.
Many of Les Amis in Les Misérables are students, though they hardly ever seem to mention going to classes. However, this is more because a lot of them seem to skip their classes rather than them not existing.
The Saturdays, the first book in the Melendy Quartet, has the Melendys form a club to pool their resources during the week so that they can take turns going into the city on an adventure every Saturday. The entire book is thus spent dealing exclusively with what the kids do on Saturdays.
Lampshaded in Wizards at War, when Nita convinces her former grief counselor from school to cover for her, Kit, and Dairine when they need few days to focus on dealing with the mysterious force threatening their universe.
The works of Enid Blyton and Arthur Ransome generally got around this problem by always setting the adventures in the long summer holiday, or occasionally the Christmas break. The only problem was the Comic Book Time issue of having ten such adventures in a row, each in the next year's summer break, without the characters seeming to noticeably age. The only time schoolwork is generally mentioned are the characters talking about having to do annoying holiday essays and, interestingly specifically, when they have to use their knowledge of schoolroom French when they find themselves in a foreign country.
Subverted in Beetleborgs; one episode involved them having to keep ducking out during class.
Awkward. is the same - they walk around the halls and go to the cafeteria and gym, but they never sit in a class or do any schoolwork.
They are shown in generic classrooms occasionally, but only if there's important dialog in the morning announcements.
iCarly averts the trope, with most 'home' scenes taking place on the weekend or after school, and school scenes taking place before school or after school. Occasionally they go so far as to wait until the bell rings which clears out the set so the characters can have their own conversations alone. On a couple occasions, they plan out a trip based on having the weekend to do it, like in "iTake On Dingo".
Boy Meets Worldlampshades/handwaves this in one episode, despite the show not being a particularly noticable example of this trope:
Cory: You know we really should have taken more classes during our senior year. We have entirely way too much time on our hands.
Teen Wolf not only averts this Trope, but actually deconstructs what would happen if an average high schooler needed to constantly duck out of classes and miss school. The hero, Scott, was shocked to find out that he was failing most of his classes in the second season and was seriously at risk of being held back a year. Most of the cast are seen attending classes in their high school. Fortunately, the Weirdness Censor trope is in full force at the Beacon Hills High School, allowing for everything from conversations about the supernatural while in class to superhuman battles in the hallways and locker room.
Likewise in Buffy the Vampire Slayer, who due to her Slayer activities is either missing class, falling asleep in class, or just doesn't have time to study. She does scrape through into college, but eventually has to drop out when real life issues like caring for her little sister and working for a living are also added to her problems.
Surprisingly almost completely an Averted Trope in Wizards of Waverly Place. A huge chunk of the series has at least a few scenes that take place at or deals with Tribeca Prep, the "Muggle" high school the Russos attend, or WizTech, the Wizard World equivalent. And the Russos attended their wizard homeschooling (or in the case of Justin in the final season, taught wizard classes) roughly Once per Episode.
A college example - Billie in Charmed. It's mentioned a couple of times that she's failing a lot of classes and one episode has her missing an important test because she's been fighting a demon. It's likely she only goes to college because the sisters make her.
Pretty much averted in House of Anubis. There are many scenes that take place inside the school- enough that the plot may often depend on these scenes. The times when the characters do skip school, they're usually always caught, or it's lampshaded. Some fans have also pointed out that the teachers do less in school than the students do, which sort of inverts the trope.
Entirely subverted by the basic premise of A.N.T. Farm which almost entirely takes place at school (to the point where, in Season 3, they move to a Boarding School).
Likewise subverted by the entire premise of Suite Life On Deck where they're living on a floating boarding school in the form of a cruise ship.
Final Fantasy VIII: You have to graduate before you're allowed to adventure, since the "adventuring" is done as a member of an elite mercenary force.
It seems that most child trainers in Pokémon stay near home until they're a certain age (usually late teenagers, post-school most likely) and are seen going to school or referring to it. You are usually eleven years old and are allowed to venture off around the region, but it seems that you were either home schooled or you finished.
At the end of EarthBound, Ness's sister Tracy says that she'll help Ness with the homework that he missed while off on his adventure. Also, when calling Ness's mom, she will occasionally remark that one of his teachers stopped by, and that she covered for him.
RaidouKuzunoha wears a school uniform and is said to be a student, but never seen at school. Given Raidou is 17, the time period (~1931), in both games he is working as an apprentice and time seems to have passed in the 2nd game, he likely doesn't need to be.
In Bangai-O, Riki's prolonged absence from school (to defeat the Cosmo Gang with his sister Mami's help) eventually results in his health teacher tracking him down. With one of the Cosmo Gang's robots. Not that the former cares, since he's technically training to become a policeman...
The below-mentioned example from the Pokémon anime is inverted in Manly Guys Doing Manly Things, where Jared's parents thought of him as a failure because he actually wanted to stay in school rather than become a Pokémon trainer.
Averted in Modern Day Treasure Seekers, as the kids sneak out at night when they have time to go adventuring, and it does seem to affect them. Cade even complains of having school the next day, and ends up very tired as a result of staying up so late.
Phineas and Ferb goes even further, since the only reason for their actions is that it's summer, except of course for the other holiday break episodes and the Halloween Episode.
South Park: Along with deconstructing what it would be like for three eight-year-old boys to watch one of their closest friends die, "Kenny Dies" actually addresses all the school days Stan, Kyle, Kenny and Cartman presumably (considering how much time they spend in places like Canada, California, Iraq, Peru, Imaginationland and Afghanistan) miss, revealing that they oftentimes cut class to go on their adventures and that this is something they do get punished for.
The Weekenders, because all the action takes place on...well...the weekend.
Ultimate Spider-Man: SHIELD has embedded Agent Coulson as the principal at Midtown High, so that if Spidey's SHIELD-operated hero team needs to be sent on a mission during school hours, Coulson can just send them to "detention."
Examples played straight:
Anime and Manga
Pokémon anime: One year passed between Ash's first visit to Viridian City and the Viridian Gym episode, and two years pass from the day Ash and Pikachu meet in the animated short that comes with Pokémon 3: Spell of the Unown. And yet Ash is still ten.
Are there any (no Pokémon training involved) schools?
There is apparently school for children under ten (though we hear this from Max who is still allowed to follow his sister across two continents, so the trope is still played straight for him), and when you reach your tenth birthday in the Pokémon World, you can become a Pokémon Trainer. People who don't want to be Trainers just continue with normal schooling. There's various fan explanations for this, but however you twist it, that's just how their world works.
Probably justified considering the average Pokémon's abilities.
For a long time after escaping from their evil parents, none of the Runaways attended school, even when most of them were still under 16. They reluctantly agreed to enroll Molly and Klara in a home-schooling program based on the curriculum at Avengers Academy, in exchange for not getting their hideouts raided by the Avengers every few months.
Jommeke: Jommeke and his friends are often seen going to school, but when an adventure takes place they travel away without any problem. It's not even addressed.
Played straight in most Nancy Drew series. Nancy's boyfriend Ned and his friends Burt and Dave are in college, but eighteen-year-old Nancy and her best friends Bess and George are high school graduates who never really even discuss the idea of going to college, or any sort of career plans... except in the short-lived Nancy Drew on Campus series, in which the college setting was the whole point. This made perfect sense in the earlier books, as in 1930 it would be more unusual for affluent young women to go to university or enter the workforce, but in the current Nancy Drew, Girl Detective series, which was launched in 2004, it's still never explained why Nancy, George, and Bess aren't enrolled in post-secondary education or planning for some sort of career. Nancy very occasionally takes courses, and she frequently works, whether it's a paid job, an internship, or a volunteer position, but these are always temporary things that last for the plot of one book and are never expected to lead to a degree or a career path. And yet her lawyer father hopes to someday rename his firm to "Drew and Daughter".
Oddly, sometimes appears in Harry Potter, despite the series taking place at a school. Mentions of what Harry's actual classes entailed got fewer and fewer as the series went on. Then the Power Trio simply drop out of school to go on the quest to render Voldemort vulnerable. Although, Hermione stays responsible by eventually going back to school to finish her 7th year, per Word of God. Even though it was probably the two boys that could've used it the most.
In Hoot, middle-school-aged Mullet Fingers (neé Napoleon Bridger Leep) was sent to military school by his overbearing mother for being somewhat of a Wild Child. He runs away from military school, travels back to his Florida hometown and lives in the woods with only occasional contact with his sister.
The eponymous heroine of Hannah Montana goes on tour for weeks at a time, and engages in activities and publicity stunts during school hours, such as reading to a group of preschoolers. Yet, as regular old Miley Stewart, she attends a public school and her absences are never referenced, nor do they arouse the suspicion of anyone at school. In the fourth and final season, however, Miley gets to see her best friend Lilly attend a California University she had been planning to attend all of her life, while Miley is rejected as she hadn't participated in enough school activities because she had to work as Hannah. She only seems to be accepted in after she reveals her secret identity to the whole world. In Real Life, celebrity children often have their lessons filled in by "studio teachers" while they're in the middle of large projects that can't conform to regular school schedules. Not really applicable here since Hanna is Miley's "Secret Identity" only known to her immediate family and closest friends.
Apparently in Relic Hunter Sydney Fox was a university professor who supposedly taught classes. How she managed to avoid being fired for her tendency to drop everything and go off to a remote part of the world to search for an ancient relic is still a mystery.
For alleged high school students (and later college students), the main characters of Smallville spend remarkably little time in class.
Particularly egregious in Kamen Rider Fourze. Despite the entire plot being centered around the school, the main characters are almost never in class. On more than one occasion, the main characters have sprinted out the door in the middle of class, to receive no more punishment than a disapproving look, and about halfway through the series, the characters were only ever shown in class if a teacher had a significant announcement or if Dustards or Zodiarts were about to burst though the windows.
Done quite blatantly in Kim Possible, where Kim is explicitly shown to skip school to complete a mission, but is rarely called on it since she gets all A's and can still head the Cheerleading Squad (and a thousand other activities.)
Though she also drags Ron along with her, who's shown to be far less successful.
Seeing as how her "saving the world" thing isn't exactly a secret to anyone, she probably can get away with it.
Her parents once said they don't like her saving the world on a school night.
Expressly justified for Wade — he's a genius who's already finished school up through college.
In the Legion Of Superheroes cartoon, nobody there goes to school. Alright, they could all have graduated as most are in their late teenage years, but in a flashback where they are shown in their uniforms, they all look about twelve or so. Are there no schools in the future?
We are told in the original comics that 14 year olds are considered adult by at least some planets in that future with the implication that this is common.
Also, many early Legion comics featured "slice of life" panels before the main story started, some of which showed Legion members either attending school or having tutors teach them while in their downtime.
Handwaved in Adventure 02. During the first half of the Kaiser arc, the kids do their adventuring after school, since the computer they use to get into the Digital World is in the school's computer lab. Once summer vacation starts, they decide that this is their chance to stop the Kaiser once and for all, and have the older kids stage a camping trip so that they can stay in the Digital World for several days without their parents noticing. Once school starts up, they go back to Monster of the Week after school adventures until winter break, when the plot starts moving again. This is also around the time that they start to let their parents in on what's going on. The series' final battle takes place on or shortly before New Years'.
Invoked in Tamers, as the characters literally walk out of school to go to the digital world, and their teacher is understandably deeply concerned about it all.
Ninety-nine percent of Frontier takes place in the Digital World, so school doesn't appear. To be fair, they couldn't go to school even if they tried. The commute from parallel world to parallel world isn't particularly easy. Also explained away via a time paradox. Supposedly, the entire series takes place in the span of only ten minutes in the real world.
In Savers, while it's implied that Touma has graduated from college and Yoshino is a legal adult and thus both would be working with DATS full time, Masaru and Chika seem never to go to school toward the end; whereas Ikuto at least had an excuse, what with having been raised in the digital world.
Xros Wars is similar to Frontier - Year Inside, Hour Outside is in effect, so while the story begins during the school semester, school is a non-issue because practically no time has passed. The sequel plays similarly to Adventure 02 and Savers, in that they generally learn of the problems during the school day and do something about them during breaks or after hours; it also exaggerates it slightly, in that some incidents have happened while they are in class.
Nabari No Ou: Played completely straight in Miharu and Raimei's cases - Miharu in particular misses at least two months of school after using the Shinrabanshou…and when he comes back home, his grandmother is just happy he's making friends. It's averted by Yoite, who never attended school to begin with, and later by Gau when it's mentioned that he ended up dropping out. It's justified in Kouichi and Shijima's cases because they're not actually kids.
Nero: Petoetje and Petatje often want to go on adventure along with the adults, but are told to go to school. Sometimes they do travel along with them by sneaking aboard on the ship or plane that takes them to another country. Other times they travel alone. Adhemar, a five year old boy genius, is always at school, but as a professor rather than a pupil. Nevertheless he does skip classes whenever he needs to go on adventure or save his family and friends. Often just by ending his lesson there and now.
Indiana Jones: On the other side, Archaeology class with Dr. Jones. Easy class, or easiest class? Is there a 15-minute rule or do the students just not bother showing up at all?
Most characters in Brick don't even bother with a handwave being that they are criminals/drug dealers though, this is Truth in Television. The protagonist Brenden though gets an aversion sense he has specifically asked the Vice Principal to try to keep the heat off of him while he unravels a crime.
Neds Declassified School Survival Guide: Sure they're in school, and sure, they go to class when the plot calls for it, but there are many examples where they are some how able to spend the entire day out of school and doing whatever they need to be doing for the topic of the class- and the teachers involved in the plot never mark them as skipping? (One example was the episode where Ned and Moze were dealing with a pair of sneakers in the Lost and Found, Ned wanting them, Moze wanting to return them, and they had the whole day to themselves to deal with the problem, never showing to class once.)
Amusingly semi-lampshaded when there's a dramatic moment in the hall, (hostage exchange, etc. - hey, it's that kind of show) a teacher or hall monitor will walk past, ask "Do you have hall passes?" and the action pauses while all the students hold up passes, then go right back to the drama.
Glee takes place almost entirely in school and characters do go to classes... but apparently they meet for Glee Club in the beginning of school, after school, during school, once a week, on Thursdays, Mondays, Wednesdays and Fridays, in the middle of the day, right before lunch, right after lunch, and during lunch. That's not even counting all of the times that various pairs of students have the choir room all to themselves in order to rehearse for Glee.
Veronica Mars is uneven in its treatment of this trope. Veronica handles cases during school hours, and manages to spend a lot of time at school digging up dirt on people rather than attending class. However, she frequently gripes about cases and consultations making her late for class, and on occasion the guidance counselor brought her spotty attendance record to light. And yet she still had the second highest GPA in her class. Her vice principal once gave her three days off so she could go undercover at a rival school.
The Disney Channel miniseries As The Bell Rings subverted this, as it took place between passing periods. The main characters would meet in the hallways during said periods, and have to leave quickly at the warning bell.
Power Rangers, when the kids are teens and not young adults, has a fifty-fifty chance of either averting this trope or playing it straight.
For some reason Rita Repulsa would spy on the Power Rangers during school hours, but wouldn't send down a monster during school hours. This actually covered all bases, once they had to sneak out during detention, a few times they disappeared (and no one noticed). However, school became less important as time went on, and by Power Rangers in Space barely any time was shown there even though they even went to the trouble of enrolling the guy from another planet (and how they fit it in with traipsing all over the galaxy, we don't know).
In Power Rangers Wild Force, the Rangers were either able to fit part-time school or jobs in around their superheroics (like Alyssa's college studies or Danny working as a florist) or they weren't (Taylor went AWOL from the Air Force and Max abandoned pro bowling training; it's not clear if the latter was attending school as well but certainly dropped out if he did).
Power Rangers Ninja Storm is a toss-up, depending on whether you think they fit ninja training and extreme sports hobbies in after normal school, or just attended a Ninja School in the first place. It's never made clear which is the case.
Power Rangers Mystic Force played this entirely straight; the Rangers are certainly young enough that they should be attending but school is never mentioned.
Justified in Power Rangers Samurai, where the Rangers cut ties with their normal lives (with their families' blessing and cooperation) to deal with the threat; it's even mentioned that Mike missed his graduation because of it. The Sixth Ranger, who has no such family support, must have dropped out or graduated himself because he makes a living as a fisherman.
Homestuck provides the page quote. The four 13-year-old kid heroes have skills like computer programming and novel writing that suggest formal education, but school is never mentioned, nor is there any indication that they have offline social lives. Jade has a valid excuse, as she lives on a small island in the South Pacific, but the other kids are subject to US law. Mom is rich enough that Rose might have private tutors, Bro might not care much about Dave's attendance or grades, but John would almost certainly be in public school. Likewise, the guardians seem to have "Friends" Rent Controlexplained by their involvement with the Ancient Conspiracy. Hussie's Shrug of God basically said "I don't think it's relevant enough to provide a canon explanation so the fandom can go with whatever".
One interpretation offers a justification or even aversion: most of the events that take place on Earth span only a few hours in-story, starting at 4:13PM Pacific Daylight Time for John, 6:13PM Central Daylight Time for Dave, and 7:13PM Eastern Daylight Time for Rose, so they could have attended school and then come home for the evening. It's early afternoon for Jade, but she's the enforced case anyway.
Averted with the Alpha Kids. Dirk and Roxy live in a post-apocalyptic future in which they are the only remaining humans, so they couldn't go to school even if they wanted to—ditto for Jake, who lives on a remote island like Jade. Jane is poised to inherit the Betty Crocker fortune and has been getting death threats, so it's entirely plausible she's tutored at home...and at any rate the scenes on Earth take place on a federal holiday.
Lampshaded in Cucumber Quest. Cucumber doesn't want to go on an adventure because he'll have to miss school. His dad brushes him off with "When's the last time you heard of a legendary hero going to school?" Possibly played straight with his younger sister Almond, who's accompanying him on his quest.
In the Teen Titans cartoon, quite a few heroes such as Robin, Mas y Menos and Raven should really be in school. A pass could be made for Raven and most of the others, as they have odd powers and would likely not be welcome in schools (Cyborg mentions at one point that he couldn't finish high school because of this). But what about Robin? The kid should really be in school right now. May be a case of Screw the Rules, I Have Money! considering who his mentor is. Robin is also preternaturally devoted to eradicating crime, so it's unlikely he could stomach an ordinary high school life when there's bad guys to beat down. And it's not as if it would be difficult for Bruce Wayne to say that he's being homeschooled or privately tutored or the like.
Largely averted in the Young Justice cartoon, where school attendance forms part of the plot of some episodes such as Miss Martian's and Superboy's first day at school, or Artemis being threatened with the curtailment of her "extracurriculars" if she doesn't do well in class. Subtly lampshaded in one episode, when the battleground of the week turns out to be the gym at Robin's school. (Apparently, Robin goes to school.)
Undergrads takes place during the protagonists' first year of college. Lampshaded at the end of the series.
An odd example that is both played straight and not (and sometimes lampshaded) all for the Rule of Funny is The Powerpuff Girls. When the Mayor calls, they will sometimes be at their kindergarten and have to leave in the middle of some activity... usually through the roof of the building.
Rick and Morty addresses this in the first episode, with Morty's parents angry about how Rick constantly drags Morty out of school for adventures. Rick considers school a waste of time, believing (and convincing Morty's parents) that hanging out with Rick is significantly more educational than the actual school system. The second episode dips into it, with Rick "incepting" Morty's math teacher to have him give Morty good grades regardless of Morty's attendance.
With Codename: Kids Next Door, this seems very much Depending on the Writer. The pre-teen heroes do go to classes, and very often the school is vital to the whole plot of an episode. Other times, they seem to have the day off for no explained reason. One rather hilarious aversion was in "Operation: F.L.U.S.H.", where Mr. Boss, Mr. Wink and Mr. Fibb, and the Crazy Cat Lady took over the Treehouse while the team wasn't there, only to be beaten up by the Toilenator (who they had gotten rid of by telling him to get coffee), who mistook them for the team. Leading to this:
Toilenator: I did it! I defeated the Kids Next Door! And I did it all before... (Beat) Three o'clock? Hey... Aren't you kids supposed to be in school?
(The real team appears on the balcony, looking very angry)
Numbuh One: We just got out of class.
Numbuh Four: And you're just in time for and after-school special butt-kicking, toilet-face!