Bang Bang You're Dead (2002)

For the most part it's a tale of an adolescent, Trevor, who gets picked on a lot at school. Not as much as he used to, because the year before he called in a phony bomb threat, complete with a working bomb (minus anything that would actually explode). Because of this, parents and teachers are afraid of him, and his fellow students generally avoid him, except for a group of outcasts called the "Trogs". As violence by the Jocks against the Trogs escalates, Trevor is the suspect for anything gone wrong, even though he didn't necessarily do anything. One teacher is willing to give Trevor the benefit of the doubt, and casts him in a highly controversial play about (what else?) school shootings. It all comes to a head as some other students create a plan to bring guns to school and kill everyone in the cafeteria.