Become an Investigator
The first thing to do is a bit of reconnaissance. Learn from your child the who, what, where, when, how and even why about the bullying. Keep a notebook of all the facts, and if the bullying involves cyberspace, print all the documents, including e-mails, texts, images and forum posts.
Then, go undercover. Study a copy of the school's printed anti-bullying policies. If there aren't any, try calling the school anonymously and asking them what the bullying policies are. This way, you will know what level of response to expect from your first meeting to your last.