I agree with u/ShutupPussy. Kids that young don't really care. In my opinion, it isn't until middle school where kids become little shits. You can just let your broski know if any kid does make fun of him to stand up for himself, let the teacher know, let you guys know, and to not be ashamed of himself. I remember my parents telling me "some kids aren't patient. They don't know how to behave, so they may act rashly but don't excuse their behavior. Correct them and tell the teacher when they say something mean." You can do something like that or not at all. Up to you.