My 10th grade math teacher got his start coaching football, and he was constantly making remarks like this. He would also sit up front with a ruler while you did problems on the blackboard, and he hit you with the ruler if you messed up.
I remember reading a story in High School Literature class of a man who did this to teach his daughter to type. it worked.
He used a pencil and popped her on the head every time she hit the wrong letter. Soon she was writing without mistakes.