As a former teacher and mother and grandmother (all boys) all I can say is that you will go mad trying to find out who started it, what actually happened, where any blame lies. Even if you hear or see the incident at first hand, you have no idea what happened previously. Schools aren't courts of justice, they are places where children should be given every opportunity to grow up. If I were the mother, I would be worried that the teacher will not let this go, and I would be even more worried that my son was getting upset about going to school. If the head is any good, she will also be worried by learning this. Sorry, grannya, it's one of the worst things to deal with and parents who try to be objective and rational are often at the mercy of teachers and other parents who are far from either.