He shouldn't have invaded your privacy but you set yourself up for a fall. Every classroom I've ever been in had a clock on the wall. Next time check that if you need to know the time. The only thing you need to worry about is if he calls the cops for the beating video, especially if anyone in it is identifiable.

Oh, and I'm sorry that your parents don't give a shit. Maybe if they did you wouldn't be beating up random people.