The teacher had given the class an assignment.

He stresses the importance
of this particular assignment, and that no excuses will be accepted except
illness (with a medical certificate) or a death in the immediate family
(with a note from that member).

A smart-ass student pipes up:
"What about extreme sexual exhaustion, sir?"

The class breaks up laughing, and when they settle down the teacher
responds with: "Well, I guess you'll have to learn to write with your other
hand."