What's the stupidest rule your school ever enforced?

No jackets. My school was using a wing of a building under construction as additional classrooms and you had to take a bus from the main building. In the winter you could not wear or carry your jacket around prior to your class in this building, so you had to spend your passing time visiting your locker to pick up your jacket and hope you make it to the bus in time to not be late to your class. The school was not small so I was frequently late or didn't wear a jacket.