I forgot my (completely pointless and unrelated to anything we were doing) maths homework, and the teacher made us stay behind during break and colour in every single tiny square on a piece on graph paper. It started off all good fun, but then it got really, really boring. Like doing lines, but even more monotonous, especially as we couldn't talk to anyone else. 10 minutes of pure torture.
...
It didn't stop me from failing to do any subsequent pieces of homework though, although I never did have to colour in squares again...
...
Oooh, which reminds me of when I was in year 7 and kept talking to my friend, and my teacher made me write out loads and loads of lines saying something like "I must not talk to [friend's name] while Mr [teacher's name] is talking, as he can do [some maths technique I've forgotten what, I think it was something to do with algebra?] and I can't.
Then once I've finished [feeling quite impressed with myself] he proceeded to scrunch up the paper and throw it at me, in front of the whole class. :L
My teachers are genuine sadists.