Yes. First, find out what the district policy is in Bullying and Harrasment. Write to the principal and copy the superintendent and ask for a written copy of it. This will put them on notice that you are going to move through the process to get something done, and you will probably get a call from the principal to find out what the issue is, if they do not already know.
Speak to him, but make sure that you still get a copy of the policy in writing. When you get off the phone, send the principal an email confirming your conversation that documents everything you said, everything he said and any agreement that you come to (if he offers to have someone investigate, says he will get back to you on a certian day, etc.) At the end of the email, say "unless you correct me in writing, I will assume that all the details I have written here about our converstation are accurate. This will send a second message that you are not going to let this rest and that you understand the importance of a paper trail. Again, copy the superintendent.
If there is no documentation of the incidents in question, send a letter confirming the details of what happend to your child. Again, copy the superintendent. You want all the administrative parties to be on notice that there is a problem, which triggers thier affirmative obligation to correct the situation and creates liablity for each of them, based on thier knowledge.
If it did not happen in writing, it did not happen.
Know this though, confidentiality applies to the other children as well as your own, so you may not be entitled to know the details of what they do to the bullies.
If there is any electronic device involved, you can involve the police and press charges yourself. Capture the offender (use the phone company to trace blocked calls and make a police report, then press charges against them.)
It is all about what the administrators know that you can prove that they know.
M.