Black sheep is right. Keep a record... and please, if you can't tell your Mom, report it to the police. I'm a Mom, and if anyone laid a finger on my son I'd want to know about it. I don't know what your Mom is like, but hopefully she's got the grit to ... how can I put this in a feminist way? Sorry, can't think of another way to put it... she has to "man up", she has to stand up and face the truth. Your Mom should always love you first, and if you can't tell her, then perhaps the police can.

At least then you are protected, he's less able to start on some other kid, and at least you know where you are with your Mom.