I think the only good deed you did was to drop him home !
Dont think of the world and correcting it ways..let ppl realise their own mistakes ..coz every one is damn well sure of what he or she is doing and pretty well aware of the consequences too ..

Incase you thought telling his parents was a good idea .. it can go both ways ..you take credit from the parents and loose a friend too ..

have fun and what were you doing at 3 am in the morning by the way ??