No matter what the child's disabilities or problems you have to protect your own children, and need to talk to someone now before one of your children really get hurt. This isn't being insensitive because this child is different, these our your children, and you have the right to protect them and bring this issue to the teachers attention, or better yet the principal's!! Don't wait, and regret it when it's worsens, if no one comes forward how does it get fixed, be the one. It's possible that this kid is teased alot, and he happens to loose his temper, and even though it's not your children doing the teasing, they are the ones suffering for it?? Once my son was threatened to be jumped at his school by a group of others due to something accidently in gym, and I went right to the school, and told the principle my son wouldn't be returning until she talked to all these boys, and assured me he was safe to come their, and I did just that, the principal took care of it, and called to assure me he would be safe, and so he missed 3 days, but he was safe, and wasn't told to go somewhere it wasn't!! Most teachers and principal's have no tolerance rules, and understand, and their's a few that won't make big deal of it, but it's up to you to get to the end of the hitting, and protect your kids! Good Luck, and remember it's about your children, and they need you to help and protect them, you wouldn't be psycho or over barring for speaking up, trust me!!