i wouldnt have punished him at all, congratulated him. he was being picked on and he delt with the situation accordingly. i even would jhave encouraged him todo more. i was teased at school till i put my fist throu a desk, then noticed someone else ebing picked on (fight nearly broke out) i stepped in, they came for me, 6 of them v me, one ended up chucked head first into a brick wall the other was lifted off the ground by his collar and was about to get KO'd just as a teacher stepped in (the whole thing happened outside her office). so yes. id say to harsh, but if i were him i would have done more... and when in that situation i did. and my parents said i handed the situation well. i gave the 6 the oppertunity to walk away. they didnt. id be putting your child into self defence classes. it worked for me and for the record. this wasnt at some dodgy school. its a private school which "doesnt tollerate bullying"
in my defence, in the lead up to all this, i gave the school/teachers many oppertunitys to curb the bullying.. years infact. then i snapped. if i were your child id have turned around and decked the kid.
thats just my opinion from personal experinces tho.
ps. im not an angry person. i just dont like the fact this school which will not be mentioned says they dont tollerate bullying. yet when things were bought to there attention they literally did nothing to stop it