I know where MDMA is comming from, and the key to that is the part where he said "When he was angry" and this part is of absolute importance, by all means chastise your child, physically if necesary. But do not resort to smacking *whilst angry*.
As for PowerAmiga, You kids teacher is talking bollox, and your kids need a good clip. I watched very very closely what was actually decided on this issue, which btw I don't think comes into force next year, but basically its just a rehash of the previous law, a quick slap is ok, beating them liberally around the head with a rubber mallet isn't. Though I suspect that the latter is in your current crisis a damned tempting option, well, for the teacher at any road.