There was a lad at my school who was a bit fucked in the head:
he threw a big, heavy, wooden metal-tipped window pole out of a 3rd floor window. He missed his intended target.
he stole £150 out of another student's locker. The student was due to go on holiday after school, and he had the money sith him to change into the local currency. Had to cancel his trip.
he tried to set fire to a teacher's car.
he spread rumours about other student's alleged sexual escapades.
he routinely robbed money out of people's bags while they were playing sport.
he brought a real looking BB gun into school and shot a few windows put.
He was only ever done for the pole throwing and was immediately kicked out of school, as he could have killed someone. He was never officially punished for the rest, but everyone knew it was him.
Last I heard the lad was in hiding someone in mainland Europe for being part of a drugs smuggling conspiracy.
Others:
25 year old teach sacked for sleeping with a 16 year old girl
two gay kids caught 69ing the toilets by a janitor. The janitor told another student about it. The janitor was fired. The two gay kids were never seen again after a period of bullying.
someone brought a penknife into school and was running around the football pitch with it, just 'having a laugh'. He accidentally ran into his mate and stabbed him in the liver.
the two ugliest teachers imaginable married one another. As far as I know they still teach there.
kids from my school and kids from another local comprehensive occassionally got into organised fights with one another. Police were called a few times, and eventually everyone from my school was prohibited from going to one bus stop in particular.
someone found a bunch of syringes in a park and brought them into school and left them around. Never found out who did it, and few days sections of the school were out of bounds while searches were conducted.
not my school but nearby: a teacher murdered and dismembered his wife. He turned upto school the next day and acted like nothing happened, and then return home to make the 'shocking discovery'. He was eventually jailed for life.