Apologies for length.
My school had an english classroom which was a small detached building.
My mate who is sittng at the back breaks wind, (cue giggling), teacher asks who it was, he owns up and the teacher says "I think that you need to go to the toilet", he says that he is ok now, teacher says "I was politely asking you to get out of my classroom".
He goes and stands outside, about 5 minutes later the headmaster comes past and asks him why he has been sent out - priceless.