I didn't want to hijack a thread. But your post hit a sore spot for me.
Your boys and for that matter nobody deserves to be bullied like they are.
I've dealt with several issues with my children being bullied, physical, emotional and racial.
Almost every state has anti bullying laws for the schools. I'll post the link for you to check your state at the end of this post.
You and your boys are not alone because unfortunatly it happens all to often. And I'll also bet the same children bullying your boys are also doing it to others. Children can be cruel and its unfortunate because they learn it in their own home. Chances are they may being bullied themselves.
I had to put 1 of my children in therapy due to bullying. Keep an eye on those precious boys of yours. Give them lots of love.
olweus.org/public/bullying_laws.page