Classroom rules work best when there are few of them (three to five), each is observable and specific ('raise your hand before speaking' rather than 'be respectful'), and they are explained -- with reasons, not just stated -- on day one. Students comply more with rules they understand the purpose of than with rules imposed arbitrarily. Consequences should be proportionate, known in advance, and applied the same way regardless of which student breaks the rule; inconsistent enforcement is the fastest way to lose a class's trust in the rules altogether. Rules should also be paired with positive reinforcement for following them, not just penalties for breaking them -- classrooms that only punish tend to see compliance drop over time, while those that notice and name good behavior sustain it.