R.C.
I truely feel for you in this situation.The schools are absolutely NO help when this problem occurs.To them it is a he said she said situation,when in fact IF they paid a little attention,they would SEE what is going on.But as with many situations nowadays,it is just easier to look away.I've been through the same problem at one time or another with each of my boys and I've done the same thing you have,HOWEVER now that I look back,this may be why my oldest has so much built up anger and will just 'go off' when he feels he's placed in this situation now(he's 19 and in the real world now,so this is NOT a good thing).
Okay,now I'm gonna say something that no-one will agree with,there are 2 weeks left of school,right,when THAT boy touches him(he must touch FIRST) tell your son to knock the 'poop' out of him!!!Now when this happens,you MUST be prepared,because I BET you,some one will intervene and your son WILL BE the to get in trouble,why ,I don't know...it just seems to be the way it happens,you try to teach your child the right thing...but then when he gets to school it seems if all that goes out the window,'cause no-one to 'back'it up.(again another rant for later)
I guess I'm just saying,there's not that much time left in the year and if he's/you are gonna let him do something,DO IT NOW.
Good Luck and Hope this helps,R.