Quite honestly it is not a laughing matter. It's not funny, it is a criminal act. Doling out drugs to unsuspecting victims is despicable behaviour. Granted they are kids so it is good that the error of their ways has been pointed out and nipped in the bud (pun intended) so to speak. But the repercussions of the incident will be long term and far reaching.
The main culprit could be expelled - is that teaching him a lesson or is it too harsh a punishment?