It was the end of term in June and the students were doing their exams. I was in charge that day and, as usual before the start of the exam, I told the all student the rules: no talking, no mobile phone and so on. I was walking up and down between the rows of desks when suddenly my own phone rang. That was bad enough, but the phone had a really silly ring tone. It took me ages to find the phone in my bag and my face went bright red One of the students was laughing so much that she fell out of her chair.