It was before my time (mid 80s), but a Home Ec teacher was shot. Her estranged husband came into the classroom with a gun. She managed to convince him to go into a storeroom with her, so the children wouldn't see anything. He wounded her, but then ended his own life. She was still there in the 90s when I attended, and her son was in my year.
There was also a kid stabbed in the leg on the school oval (not fatally or anything). It was pretty universally agreed by us kids he deserved it, because he was well known to be an hole. As a result, they changed the school hours to finish earlier, and we only got 15 minutes for lunch.
Not really a scandal as such, but a lot of the teachers were utterly bizarre. There was an elderly teacher who'd buy and sell weed from/to students. He'd often fall asleep in class too, and spoke so little English that even when he was awake, there was no point to his lessons. Another brought her snakes to school in a teapot. It was an odd place, although the folks I've kept in touch with all seem to have turned out alright.