Sometimes, people have the right idea. Other times, they're just being plain stupid. Post whatever someone in any class of yours has done that you thought was so stupid you had to try not to laugh.
I'll start.
Today in algebra, we went over a review quiz we took on monday. We came up to a simple problem, 8x6. The teacher jokes around a bit, saying, "If you got this one wrong, when you go home today, y'know...hurt yourself." Almost everyone in the class laughed at, but the person next to me took it seriously and got pissed. He proceeded to moan and hit himself.