That totally sucks for you and your friend, I feel for you bro. This is one of those problems that really does not have a 'right answer' imho. Try to keep in mind that he isn't totally 'in control' of himself, sounds like he has the monkey-on-his-back of addiction to hard drugs. He probably has deep depression and/or other mental health problems - using hard drugs all the time can cause many mental illnesses. His thinking may be that he is a piece of shit and will probably kill himself - so who cares if he doesn't do anything, steals, etc. I am not saying he actually will do so, but is using that as a crutch to deal with in his mind for the bad things he does (like steal). It's sad that his school does not pick up on that there is a problem and attempt to find out wtf is up with him. A shame. I'd not drop him as a friend and do your best to try to get him to go see someone. You don't really want him to get arrested or involuntarily tossed in an institution - that would fuck his life forever, quitting drugs or not. There are other things you can do, but they involve you 'ratting him out' to Social Services or some other agency. That step is hardcore in my opinion so I can't recommend it, I just mention it so you know. I have NO clue if my opinion is correct or even a good course of action. Again, I feel for you and good luck man - karma will hook you up for caring like you do about another human being.
thanks everyone. i'm going to talk to him friday. he's my best friend, and i just don't want to see him fuck up like this. hopefully i can talk some sense into him. and i definitely get the whole "he's addicted to being high" thing. that's probably the best way to explain it. because he hasn't been doing anything long enough to really become physically addicted to it. anyway, peace.