I started at school in the late 70s and finished at the end of the 80s.
The gropers and oglers were obviously the worst in secondary school.
I went to a state C of E school for primary and the headmaster was an absolute cunt. Every Wednesday morning we had hymn practise (whole school) instead of assembly. All the other teachers buggered off (probably to complain to each other about what a twat he was) so he was on his own with about 400 pupils. He played the piano and at some point during the hour-long torture he would become convinced that "those at the back" i.e. the oldest ones were "talking and fidgeting" (they never were, we were all terrified of him.) He would start to lean back on his piano stool so he could keep playing and try to spot the non-existent mischief makers. I'll never forget the day he fell off 
When I was in the 2nd yr (Year 4 now I guess) he overheard us at break time, singing "We three kings of orient are, one in a taxi one in a car". He came charging into our classroom when we went back in and spent 10 minutes giving us a spittle-flecked rant about how we were all going to hell for blasphemy. Bear in mind we were 8-9 years old. He described in great detail how the flames of hell would burn us agonizingly and how our skin would crack and go black, then satan's minions would cut off our fingers and toes.
A friend of mine who was very sweet natured and kind hearted (and hadn't even been singing!) ended up crying hysterically and her mum had to come and pick her up. She then had nightmares all night and had to be kept off school the next day.
After I'd left the school he was forcibly retired after he beat a boy quite badly, in front of the rest of the class, for saying "bloody hell".