The problem is that I'm not sure what I could ask them to do besides what they are already doing.
I think the magic words here are "deal with the culture of bullying that seems to be developing at this school." You can absolutely ask them to look into anti bullying programs and techniques that they could implement school-wide. This takes the pressure off your son as the center of attention and solves what seems to be a wider problem.
I was badly bullied as a child and intervention by authority figures tended only to make things worse. Because they brought me unwanted attention as a victim and made me more of a target.
Also, I recommend signing your son up for martial arts. I know I've posted about this here before, but again, it's been great for our DD in terms of confidence and bully-proofing (not perfect, but very helpful). Here's my previous post:
http://giftedissues.davidsongifted....Re_Intensely_Independent.html#Post185008
