Truancy is a game mechanic in Bully.
If Jimmy fails to attend a class that he hasn't yet passed, he is considered truant. Authority figures will be on the lookout for him. If he is busted on campus by a Prefect or Faculty, he'll be taken directly to class. If he is busted by a Police officer or Orderly off-school grounds, he'll be dropped off at the front gates of the school by Officer Williams.
Once Jimmy has passed a class, he can skip it without being considered truant. However, Jimmy will be sent to class if he gets busted at the academy.