Picture this: the front of the classroom in question has a classic whiteboard, then an interactive whiteboard, then another classic whiteboard. During history, our gerbil-teacher (he used to do this thing with his hands and stick out his teeth that made him look like a rodent when he was nervous) finishes writing on one board and moves over to the other. Except... he forgets to take the pen off the wall and scribbles all over the interactive whiteboard in indelible pen.
My first German teacher hit a kid with a wooden ruler when he talked in class. We got that ***** fired.
An art teacher got on the wrong side of me a few years back. Not dumb, but a heinous *****. She wouldn't start a lesson without checking my homework and finding at least three things wrong with it and loudly announcing them to the rest of the class. She gave me over forty detentions for stuff I didn't do (it was her talented artists; not like she was going to bring them in!), she was a rude ***** towards me (and I had confidence issues at the time, which didn't help), she was really fat and obviously didn't like herself because she took it out on me (and occasionally one other boy, who also wasn't great at art), she once found my manga drawings and loudly told me they were terrible (they weren't, because I entered one of them (a manga-styled Surrealism piece) into an art competition outside of school and won first prize) and that it wasn't a viable form of art and, the one that finally snapped me was, after I decided to leave that godforsaken shithole of a school, I took a taster week at my next school. During that time, she gave out, and subsequently took in, a piece of homework. She then tells me off for not being there, and gives me a detention from 4-6pm, on the last day of term, my last day ever at that school, which finished at 12pm. In that situation, you are not allowed to go home, you have to wait in school until the detention is served. When the day came, I flipped her the birdie, and walked out, never to return. What she didn't know then is that I'd left a little surprise for her on her desk: a small, unremarkable box, with the burnt remains of my art project inside, and a little note saying, "You said you wanted my project to be unique: well, I'm pretty sure nobody's done this!". Also, I traced the word '*****' in the top layer of ashes, but I don't know if she saw that. But anyway; I got a letter during the holidays asking for a letter of apology, because apparently I 'traumatized her greatly' and 'made her cry'. She probably cried mayonnaise...
I never felt more accomplished than I did when I red that letter, I tell you. Best feeling in the world.