Dear ADDitude: How Can I Protect My Child from Bullies?

"There are a few boys at school who have been picking on my son and saying they are going to beat him up, which a teacher overheard. I'm very concerned that the principal, after questioning them, sent the boys back to class without calling me. First, what is an appropriate response from the school? Second, am I over reacting? I'm so upset over this and can't think clearly."