One of my friends in High school was terrible for it.
Our maths teacher came over and was all concerned for her and kept asking her if she was okay. That was funny. We were too busy drawing on her.
Our RE teacher used to find it hilarious (she used to sit right in front of the teachers desk and go to sleep!) But then my RE teacher used to take her shoes off all the time, be obsessed with the vicar of Dibley and drew an anime image in my leavers book.
My French teacher was the best though. Again she sat right in front of his desk, and when she nodded off he crept over, went BAAAAAAAAAAAHHH! really loudly, ran across to the lights and kept turning them off and on going "Night! Day! Night! Day! Night! Day!" and then finally turned half on and went "dusk! Do you understand?"
We were in tears :,)
He was an awesome teacher though. He also chased someone down the corridor with a tissue full of chewing gum stuck under the desk, and one time got us all to hide at the back of the classroom and turned all the lights off so the head boy would think he didn't have class.