There has never been any mention of any schools that Sam and Dean Winchester have attended. In After School Special, it reveals one high school where the two boys went. At Truman High, Dean was in Grade 12, and Sam in Grade 9. Both boys have different experiences. Years later they return to the school.
For Dean, school is a joke, and its just a way to spend his time while waiting for his father to come back. He demonstrates this by not bringing book or anything else to class. He even calls the teacher "sweetheart". Dean starts out as the cool, mysterious, guy. He later makes out with Amanda in the Janitor's closet. By dating Amanda, he further increases his popularity. He and Sam still meet at lunch and talk in the halls. He also is still protective of Sam when he sees a bruise on Sam's face, and threatens to tear Dirk's lungs out.
Although, his relationship with Amanda begins to turn serious when she wants him to meet her parents, which causes Dean to freak and cheat on her with another girl. Amanda catches him and breaks up with Dean. Amanda also turns Dean's popularity upside down and makes him look pathetic. Dean luckily receives a phone call from John and is relived to get out of the school.
Sam has always been more serious about school then Dean. Unlike his brother, Sam brings a backpack and keeps to himself. Sam wants to be normal and not a freak (because of his hunter training). He befriends a boy named Barry Cook. By befriending and helping Barry, the school bully, Dirk, sets his sights on Sam. Dirk attempts to get Sam to fight him, but Sam refuses which results in Dirk punching Sam. When Dean finds out, Sam attempts to calm him down. Dean doesn't understand why Sam didn't rip the other guy apart, and Sam responds by saying that he wants to be normal for once.
One day when class ends, Mr. Wyatt calls Sam over to talk about his essay. He asks Sam if he had thought of going into pursuing writing. Sam answers no and that he has to go into the family business. Mr. Wyatt asks Sam if he wants to go into the business. This makes Sam think, since no one really asked Sam that before. Mr. Wyatt continues on by telling Sam to be what he wants to be and not what someone tells him to. This sets Sam on the path that will eventually make him go off to college.
He also takes care of the bully problem when Dirk pushes him too far. Sam takes Dirk down and calls him "Dirk the Jerk". Sam gets instant star status from the school population. When Sam leaves, he's sad to go.
Sam and Dean return to the school after a girl gets possessed by a ghost and kills another girl. They come back, but this time undercover. Sam poses as the school janitor, so he can scan the school. While Dean poses as a Gym teacher with really small shorts. Sam figures out its a ghost possessing the students of Truman High. The ghost is the former bully Dirk. Once everything is dealt with, Sam goes to visit an old teacher and tells him that he is the reason Sam went to college.