Ours was fairly tame compared with some of these, but:
Middle School -
We had a teacher who would slam boys heads in their desks if they annoyed him
School playing fields backed onto wasteland so MASSES of flashers
Head teacher once gave a whole assembly on the importance of us girls drying between our legs after swimming (wtf?!)
Senior School -
Massive fights on school buses between our school and the one down the road from it
Boy in my year stole the car from the MVE workshop and crashed it into the sports hall
Celing tiles suddenly collapsing onto biggest bitch in the class's head during gym class (we felt it was divine retribution)
Lower school block set on fire during summer holidays - the head seemed far more miffed that whoever had done it had drunk all the communion wine first!
Very scouse teacher with no people skills whatsoever taught a remedial class in a room next to ours - all we ever heard from next door was 'Shurrup! I said shurrup! Shurrup you little gets!' and furniture smashing...
Sex education from nuns
Physics teacher married a sixth-former 2 months after she'd left school
Art teacher playing snooker with fifth-form girls on a field trip used the end of his cue to lift their skirts when they leant over the table (could be school myth, he was still teaching there years later, but he was a pervy sleazebag, so it was easy to believe!)
However, what is beyond doubt, as my sister witnessed it, on a 'retreat' week, her RE teacher had a nervous breakdown, believed he was Jesus and appeared stark naked before them at dinner time, patting them on the heads and saying he loved them all...