1) Fairly standard one... the music teacher (not employed by the school specifically, he taught brass instruments at every high school in the area) was banging a 17 year old pupil. It was a complicated one because he was an "outside contractor" (it wasn't his main career) and she wasn't underage, etc, but he definitely wasn't allowed to teach trumpet in schools any more
2) A guy in the year above me inadvertently told everyone that he frequently shagged his dog, believing this to be totally normal. Like he just... said it... in everyday conversation... like "lol u know when you're shagging your dog and..." thinking it was just like having a wank

. People thought he was joking, and then when it became clear he wasn't, some other kid
kicked the living **** out of him right there and then.
3) This one was my personal favourite. Two teachers from the same department at my high school, in their 50's, had been together for decades and seemed totally happily married... then he had an affair with a supply teacher in her 20's and somehow the entire school found out about it. They got divorced but both of them carried on working at the school, two rooms along from each other, and sometimes they'd have to go into each others rooms to get materials / textbooks etc and it the atmosphere was like ICE!

amazing.