You have to make sure as he is a minor he gets help its not a matter of rolling with the punches, he is going to ruin his life.. get tough on him, ground him, take everything away till he stays in counseling ,whatever it takes, no going out no anything, Are they allowed to drink beer at school find out how this happened sounds as if the school is accountable here. You need professional help for him, its in your hands make him realise this behavior is not permitted in your house.
PS Where is he getting Oxycontin from and pot , where does the money come from, do some detective work and find out who is enabling his behavior because someone is, thats for sure.
this sounds exactly like the situation with my brother, sean. he got into pot, then went on probation, and now is smoking cigarettes, and doing cough syrup, the poor kid, doesn't have any idea what he's doing.