Students get involved with extracurricular activities for all sorts of reasons. They let you network with other people who happen to share similar interests and hobbies, they let you use school resources for fun, and they look great on a college transcript/résumé. While there are obviously some exceptions, like performance clubs with recitals and organized sports, pretty much all non-sports-related extracurricular activities are just afterschool activities pursued casually by their members.
That's not the case with these clubs, though. In the more benevolent cases the club is simply treated as a full-fledged social institution, with stereotypes about its members and strict rules about its conduct. A powerful enough club is a political force in the school, potentially wielding power on par with the Absurdly Powerful Student Council. In the worst cases the club may actually be a cult engaged in nefarious deeds, and those who quit may have to be...silenced.
Often, particular clubs will represent a microcosm of real-world organisations;
- The Absurdly Powerful Student Council is government, the President being, well, a President.
- Hall monitors, prefects etc are police, or in extreme cases State Sec.
- The School Newspaper Newshounds and College Radio are the media.
- Performance clubs and sports clubs are the celebrities.
- Girl Posses are the wealthy socialites and The Beautiful Elite.
- Math clubs, chess clubs, or science clubs (whether general or for a specific branch, e.g. computers) are the "brain bank".
- Religious clubs are Moral Guardians or Straw Conservatives.
Note that these tropes can be different types of "serious business". It can be very exaggerated, like clubs determining all of your relationships in high school, or completely bogus, like harboring a plan to stop an apocalyptic prophecy. A Japanese School Club may overlap with this trope.
Subtrope of Serious Business.
- Bodacious Space Pirates: The Yacht club contains an inexplicably high number of exceptional people, as well as being a club which flies spaceships. On different club trips, they have operated two of the Original Seven pirate ships in battle. Their members have included the heiress to the most powerful corporation in existence, an expert cracker, a pirate captain, and two princesses, and the club possesses both a disarmed warship and a latest-generation stealth shuttle.
- In Code Geass, Absurdly Powerful Student Council President Milly is able to get every club on campus looking for Arthur by promising them increased funding, in addition to the kiss with a council member. At the end of the episode, Lelouch asks Milly to let the Japanese Suzaku join the student council by mentioning that students must be part of a club.
- Somewhat parodied and Deconstructed in the first episode of Gamers!. Protagonist Keita, an avid gamer, is invited to join the newly-formed Gaming Club by its president, Karen. When he gets there, he finds they're all hardcore competitive gamers who've won dozens of tournaments, and who work him to the point of exhaustion in an effort to gauge his skill level. The story looks like it's going to be a typical School Club Story... except Keita turns the club down as he feels it's too serious. Another boy joins at the same time Keita refuses... because he's lost his memory and can only remember that he likes block puzzles, so for him, it really is serious business.
- Genshiken: The people who decide which clubs are official are cracking down on those that don't do anything, because there are so many clubs that even the Genshiken's remote space is coveted.
- Girls und Panzer: Tankery —tank battles— is a real club, and there is even a national as well as international league for it! It's also serious in the more mundane sense: win the tournament to prevent the school from being closed down. Other clubs include ninjutsu and magic.
- Haruhi Suzumiya
- Haruhi was just another high school girl who created her own club to find aliens, time travelers, sliders and espers... AND ACTUALLY MEETS THEM! (not that she knows).
- The computer club aren't as bad, but being next door to Haruhi seems to have rubbed off on them judging by episode 12 (chronological order).
- K-On!: Invoked in the manga, when Nodoka discovers Yui isn't in a club so late in the semester. Nodoka ponders, "So this is how a NEET begins", causing Yui to freak out.
- A few episodes of Kamigami No Asobi revolve around getting the gods to join clubs. Loki and Thor pick the Going Home club, and apparently that's good enough.
- Parodied in Kyou Kara Ore wa!!: Mitsuhashi is a member of the Gardening Club, but he never shows up. And the one time he's tricked in showing up, the president (who wanted him around due the bullying the club experienced from members of a sport club) makes him an ecologist... Who promptly takes over, forces the club to leave weed in place, and beats into submission the sport club.
- Magic User's Club: Even though they actually are quite active, the magic users have to share meeting space with a different club, which causes some conflict.
- The Ouran High School Host Club consists of some of the richest and most popular boys in the school, and they have the headmaster's ear and influence over seemingly every facet of school life. Fortunately they use this power almost exclusively to stroke their own egos.
- In Rosario + Vampire, the protagonists are all members of the newspaper club (Tsukune originally decided on joining the swim team instead, but that left Outer Moka heartbroken because, well, vampires and water...), which spends much of its time investigating other clubs. The newspaper club has a rivalry with the Public Safety Commission (another club), with effective control of the school at stake. There's another club in the anime that consists of three lovesick losers who engage in such activities as creating a harmless Stalker Shrine.
- Parodied in Sgt. Frog. Fuyuki starts the paranormal club, but only has one other member in it (and she only joined because she had a crush on Fuyuki). The school newspaper also discovers the aliens' existence, but nobody believes them because they're a school newspaper (and because Fuyuki managed to confiscate their evidence).
- Invoked and lampshaded in Twinkle Saber Nova, where students can get away with literally anything (like trying to take over the school, or demolishing half of it in battles involving Powered Armor), as long as it's a club activity. And to make it a club activity, they only need three members to register their "club".
- Kill la Kill takes this Up to Eleven. Student Council President Satsuki Kiryuin uses school clubs to control the masses by offering them social mobility. Since she's effectively running a fascist state inside Honnouji Academy, she also turns the student clubs against each other whenever she thinks they're becoming too complacent.
- Subverted in Five Weapons, since the weapons clubs are pretty much the classes in the School of Five Weapons. However, they are clubs in the sense that even though most students pick one club and stick to it, students are free to join multiple clubs to decide which one they like best.
- In the Young Adult novel The Lottery, by Beth Goobie, a High-School club known to the staff as 'The Celts' but to the student body as 'Shadow' arrange a lottery to select a 'victim' for each year, who is ostracised by the entire school body for the rest of the year, and who has to do the 'Shadows'' bidding. They manage to prevent the students protesting by a mixture of offered prestige in joining shadow, and the threat of becoming the next victim or being humiliated if they speak out.
- In the teen novel The V Club, a wealthy woman leaves money that would provide a full scholarship to one lucky high school student, on the condition that this student be "pure," which everyone interprets as "must be a virgin". (It should be noted that neither the deceased woman herself nor her attorney specified exactly what she meant by "pure;" everyone just assumed she meant virginal.) The students who are vying for the scholarship join a club (and losing one's virginity means being kicked out), and take a pledge to abstain from sex. Not everyone competing for the scholarship actually is a virgin, however.
- In one Blue Bloods a sinister college club develops the ceremony of ritually "hunting" female students as if they were trophies. One member actually volunteers to rape his girlfriend on the grounds that he would be more "humane" then the other boys. It never seems to have occurred to him to warn his girlfriend or go to the cops until the cops actually caught him. His school club was just too important.
- In Buffy the Vampire Slayer, Buffy tries and fails to join the cheerleaders. Someone else is so intent on joining the team that she's trying to kill people to get on, and so does Dawn, though there was a different spell in there.
- In Community, Greendale Community College is full of these, ranging from the debate team and the glee club to the Model United Nations. All of them turn their pet interests Up to Eleven. The study group itself qualifies, despite being informal; it has a waiting list for membership and the Dean treats them as a school power faction.
- The glee club in Glee is VERY unpopular, and anybody in it are social outcasts, a plot point in the series. They also occasionally start spontaneously singing in hallways, drawing the school's attention. By contrast, the glee club at the boys' school Kurt transfers to are revered celebrities.
- School clubs give gameplay benefits in Disgaea 3.
- In Persona 3 and Persona 4, joining clubs can start several social links, and the characters involved in the Social Links can be altered depending on which club you join.
- School clubs are an extremely important part of the Tokimeki Memorial series. Most of the winnable girls being members of specific clubs, joining their respective clubs is the only way to get some of their special Events and CGs. Also, School clubs give you powerful special attacks for battles; perfoming well in the club during the School Festival and, in the case of sports clubs, winning matches and Inter-High tournaments net you big Relationship Values towards the girls; and becoming the Club Master of the Science Club allows you to unlock the Shooters mini-games.
- Fillmore! runs on this trope, along with Absurdly Powerful Student Council. The Safety Patrol has the power to arrest and punish students on their own, what else needs to be said?
- The Grim Adventures of Billy & Mandy had an episode where Billy, Mandy and Irwin joined some clubs during their school's "School Club Recruitment Day"—Irwin joined the macramé club, Billy joined the Junior CIA Club and Mandy joined the Secret Snake Club. The members of Mandy's club believed in a snake-god that they thought would eat all the "cool kids" at their school while Billy, who quickly became a top agent for the CIA, discover that Irwin's macramé club was being used as a criminal front.
- A Funny Background Event that happened when Mandy by talking to the members of Secret Snake Club was the student at the table for the school's glee club was crying. Think about that about for a little bit...
- Pops up occasionally in later seasons of South Park (although as a rule, it's more often the adults who get carried away by Serious Business).
- In one episode the boys' school news broadcast gets into a ratings war with Craig's Lowest Common Denominator "dogs in hats" clip show.
- In another, Cartman hijacks his morning announcements slot to run a smear campaign against student body president Wendy and get himself elected in her place, only to find out it isn't anything like the Absurdly Powerful Student Council he thought it was.