I'll give you the benefit of the doubt and assume you're for real.
Don't expect too much from a 30 day detox. If he still has the attitude that he wants to use (more likely than not), he will jump right back into the same old routine.
Get him out of that school. Since he's been gone for 30 days, this semester is shot anyway, and it sounds like he wasn't putting much effort into school. Find out if you have local charter school options or online school options, if he's even willing to do school of any kind. If he's not willing to do any sort of school besides the one he was attending, tell him he's not going back to that school and that he needs to get a job. Sitting around doing nothing all day should not be an option.
How does he get car keys? Those should be locked up. Where does he get money for the things he's been buying? Assuming he doesn't have a job, he's either stealing, dealing or both. Lock up anything of value before it just disappears (been there done that). Why are you threatening to cut off guitar lessons? The guitar should be gone. Cell phone? Gone. Computer, internet, video games? Gone. Offer him little more than food, a roof over his head, a willingness to pay for therapy and of course your love & support. Write a behavior contract, spelling out the rewards he can earn for responsible conduct (i.e., earning back the things & priveleges you took away).
If he doesn't like the psychologist he's been seeing, find another one. And another and another until he finds someone he feels comfortable talking to. Otherwise you're just wasting your money and his time.
Prepare yourself for the battle of the century, but try to always be looking out for ways to praise him verbally reward him when he acts responsibly or says or does something positive. Try not to engage him or argue with him when he picks a fight. It's so hard to do, but the argument itself may be a 'reward' for the very behavior you don't want to reward. If he gets physical, tell him to leave and go for a walk until he calms down. If he runs away, let him run. He will come back.
If you just let things go on as they were, there is a good chance that he will eventually have a run-in with law enforcement, either directly or via the school authorities. That will put him into the juvenile justice system and will put you in a position where you have a lot less influence on what happens to him.
If you put him in a program, there is strong possibility he will come out a lot more damaged than when he went in. The best you could hope for is that they do no harm, but understand that they aren't really going to help either. Oh by the way, going the program route also means parting with your life's savings and/or getting a second mortgage.
Good luck to you and your son.
