Ah, schooldays. The excitement of thinking "how specialsed" when you hear sex education is to be given by the head teacher. The trepidation when you find he's male. The relief when your misunderstanding is explained.
You must have been in the same sex education session as me in the school hall for the entire Lower Sixth. Far too late of course. We got in the Head's group: Head: You can ask me anything. I'm very broadminded. First pupil: Can you get VD from a toilet seat? Head: Er, oh um, er ..... Suddenly he had a lot of filing to do in his office. He never answered the question.