Schoolday's over. Students prepare to leave... But not all of them go to meet friends, hang out with friends/a Love Interest or to a family. For various reasons, some live alone, younger than you'd expect. The most common cause for this trope is that their parents are dead or absent.
Children that live alone are sometimes rather mature for their age and may even have a job in order to support themselves. If they live with younger siblings, expect them to take on the role of Parental Substitute.
Related to Parental Abandonment. See also Emancipated Child, where the child divorces their parents and goes to live on their own, Department of Child Disservices where child protection services being crappy in general, including this trope as well as placing kids with bad foster families, and Social Services Does Not Exist which is about kids not being taken away from bad families.
Anime & Manga
Orihime from Bleach lives alone. She and her older brother ran away from Abusive Parents and he died in a car accident. Word of God is that she receives money from relatives although she gets a job after the Time Skip.
Haruka from Free! lives alone in his late grandmother's house, although his best friend Makoto does live right down the street. Haruka's parents moved away for work, and his grandmother died sometime later.
Although she has friends and family she could stay with if she wasn't too polite to ask, Tohru decides to try to live on her own after she's orphaned. In a tent. Fortunately, the Sohmas are persistent enough to get her to stay with them...although one could just as easily question the logic of moving in with three guys she barely knows.
Momiji was forced to leave his parents when he was about eight, and by the time the series begins, he has a house of his own on the Sohma estate. There would have been plenty of servants around, and Hatori seems to look after him when he has the time, but he's very independent by the time he enters high school.
In Kamisama ga Uso wo Tsuku, Rio, not yet in junior high, lives alone with her little brother. Their mother is deceased and their father is always on long trips for his work (or so she claims).
Midori no Hibi: Seiji lives alone, since his parents are said to be traveling abroad and his older sister, Rin, lives with her boyfriend. She drops by, every other month or so, to give him enough funds to cover food and expenses.
The title character has lived alone his entire life. His only supervision comes from his academy instructor, Iruka (who doesn't go to his home) and the village chief, who stops by drop off money for the month's expenses.
After the slaughter of his entire clan, the deuteragonst Sasuke lives alone as well.
Justified in Onegai Twins, Mike was allowed to live alone thanks to a deal he made with his orphanage, which let's him work and live alone.
Mami had parents died in an accident. As it turned out, she also had no relatives, and thus had no choice but to live on her own.
Homura, whose family is either nonexistent or estranged. However, her reasons for living alone also stem from the fact that she came to the conclusion that she can only work by herself after countless failed time loops.
Kyouko lives in her apartment complex alone with no parental supervision due to her father murdering her mother, younger sister, and then himself in a murder-suicide.
Ukyo Kuonji of Ranma ½ not only lives by herself, she runs her own business, all while still being in high school.
Makoto Kino from Sailor Moon lives alone because her parents are dead.
Rei Kuroki from Vividred Operation lives alone with her pet parakeet in her apartment complex because her parents died from an accident.
Runaways is about well, Runaways, the youngest being eleven at the start of the series and the oldest starting at seventeen, that have superpowers and live alone after running away from their super villain parents and then again from child protective services that wanted to keep them apart (and put their dinosaur in storage...It Makes Sense in Context).
In Angel 15-year-old Angel lives alone and is a schoolgirl by day, hooker by night.
In The Little Girl Who Lives Down The Lane the eponymous Little Girl is living alone in a big house after her terminally ill father committed suicide and she killed her estranged/abusive mother who had come to take her back.
In the novel and Film of the Book Hugo, the titular 12 year old character is living alone in a train station after he was orphaned and his uncle abandoned him.
This is the state of affairs for the eponymous character in the second Jack Blank book, and he's only thirteen years old. However, Jack lives in the Imagine Nation, which is a fictional country that functions as a safe haven for superhero fantasy, so the laws may be different there. Even so, 13 is still quite young for someone to be living alone.
In original Sims if a parent died a child would live alone...but couldn't pay bills, cook meals, or do anything for themselves.
Almost Averted in The Sims 2 where the social worker would pick up orphaned kids. Orphaned teens however, could live alone and could at least pay bills and cook, unlike kids.
The Sims 3 continues the " orphaned teenager can live alone" trend. However now teens can get part time employment so it's much easier for them to have a steady cash flow. They can also register as self employed with the Ambitions expansion pack, almost eliminating the need for parents.
Homestuck: Roxy and Dirk (age 16) each live alone, due to being the last two humans alive.
Alvin and the Chipmunks: For the first three seasons, The Chipettes lived in a fully furnished tree house, with a living room, a kitchen, bathroom, and bedroom, however, in the Season Four opener, school officials find out about this, and threaten to split them up and put them in foster care; Dave temporarily adopts them, however they and The Chipmunks start getting on each other's nerves, so Alvin talks Miss Miller into adopting them.in one episode.
Hey Arnold!: Played with: Gerald is fed up with his family not giving him enough space, and moves into an empty room in Arnold's home, which doubles as a boarding house to live by himself. He only wanted attention for leaving though, but his parents and Arnold's Grandpa agree to let him stay until he decides to come back on his own. He moves back by the end of the episode.
Recess: Played with in "Bachelor Gus", in which Gus overhears what he thinks is his parents talking about moving away (again), and not wanting to move again, let alone leave his friends at Third Street School, he runs away, and turns the jungle gym into his own bachelor pad. He likes it at first, but is scared by nightfall, and when his parents find him, he learns that they were talking about moving him into the bigger bedroom, not moving away altogether.
All of the Teen Titans live without parental supervision in their island headquarters and they fight crime. It makes you wonder if maybe their city lacks a child services department.
Five hats means that five tropers think it is ready to publish.
You are saying that you think this draft is ready to be published. That means the description is not ambiguous,
it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.
Is that what you meant to do?
You are saying this draft has a ready-to-publish hat it does not deserve and you are taking it back.