If I was asked to do a 5 minute presentation to a group of school children I would talk about bullying, and the effects it has on others. It is something that they have heard a hundred times, but it is also something that they can't hear enough. I would try to make them empathize, relate to how it fees, and show them the long term effects it can have. I would want to help them understand that being cool is about being nice to 'everyone' not about being tough.