Someone made this exact same thread a few months ago, so copy-paste from that:
We used to have this teacher who would lose her rag so much when she started shouting that she had a heart attack one day. She never came back after that (she didn't die, I mean she never returned to teaching in our school).
Some guy in my class was diabetic and had a little blood sugar testing kit, the school psycho got hold of it and pricked about 10 holes in his own fingertip and started running around, pressing the bottom of his fingertip and spraying everyone with blood - teachers, pupils, everyone
There was a fight outside the canteen, a teacher tried to barge in through the crowd and break it up but she got knocked down the stairs and broke her back.
There was a fight in the canteen and one of the guys was clearly a wrestling fan - he German Suplexed the other guy through a lunch table and it broke in half, properly authentic WWE style
Two girls were fighting and one of them must have had change in the top pocket of her coat as change flew out everywhere and everyone started scrambling.
On another occasion, two girls were fighting and one of them was a f***ing ANIMAL - the other girl had loads of bald patches after having handfuls of hair ripped out, and her shirt and bra got ripped off and everyone could see her tiddies
All the guys started booing when the fight was broken up by a teacher who put her coat over the girl to cover her up. Must have been humiliated.
It was sort of a thing in our school that people would just fight until a teacher broke it up as they'd always be along, but one day there was a fight at the gates at the end of the day and the teacher that was in charge of unlocking the gate that day must have forgot it was their turn as they were 15 minutes late, so the fight went on for a full 15 minutes. Both guys faces looked like cauliflower by the end and they were totally exhausted!
There was a fight in a 2nd floor room and one of the guys was literally trying to throw the other one out of it! The teacher managed to break it up before anything really bad happened.
Lots of instances of people getting "swirlies" (head flushed in the toilet).
There was this really quiet kid who never spoke to anyone apart from his one friend and the teachers, always kept himself to himself and didn't seem like the type to defend himself, but he always got left alone. Then one day someone threw a can of coke at him and it soaked him, so he chased them down and beat the living crap out of them and put them in hospital. He was never punished for it!
There was a Russian P.E. teacher with a very thick accent who everyone used to mock mercilessly for it, until one day he pinned a guy up against the wall by his throat and got the sack
There were various cases of minor arson, and people always used to chuck chemicals and stuff around in science.