Looking back at my school years, I can think of several teachers right off-hand who seemed to get turned on by punishing kids. That's pretty sick.
In my 9th grade Physical Science class, a kid was working on a report for another class. He was about three or four pages into it when the teacher quietly walked past him and took the report from him almost before he noticed, and put it through the shredder at the back of the classroom. He put his head down on his desk and started crying because he was almost done with the report, and he was going to fail the class since it was just next period and he needed that one passing grade to pass for the year. The teacher just gave a smile and said "Shouldn't have been doing that in my class" in an airy, taunting way.
I guess teachers really do abuse their power sometimes.
My Mom would have had me switch teachers if some shit like that happened.