krupski,
I hope your teacher catches you now that you confessed. On the other side of the fence, a retired colleague of mine used to charge up a large capacitor, realizing some of his students has fallen asleep during lecture, then discharged it with a metal piece. The loud bang woke up everyone, very angry. That's how he got back at the sleepers. I bet he'd use a ruler to slap them if they still allowed that. Waste of money, I say, to sleep in a classroom.