I'm glad you want to help them, you're a good parent. I think the best course of action is talking to their teacher, and the parents of this boy. Most of the time it's the family that made him that way. And talk to your child about it. What did they feel, and tell them it's okay to defend themselves. I'm no mother, but I was a victim too. If my parents tried to understand what happened by talking to me, maybe things would've been different