I have just been listening to a discussion on Jeremy Vine's show on the sexual bullying of teachers by secondary school pupils. It was actually quite worrying and made me very glad that at the age of 22 I reconsidered my original plans to be a German teacher. But one anecdote from the programme did make me laugh.
A 14 year old boy in a class put something down his trousers and thrust his crotch at his female teacher. She looked up and said: "No thanks, I'll have a cigarette later."
That's the way to deal with it - ridicule. Show any sign of weakness and you're finished.