He needs to play the dutiful son till his 18th birthday and then promptly announce he's walking right out the front door.
Be there waiting.
If his parents get him to the wilderness program before... hmmm. That's tough because it's a valid fear of being stranded in a desert that forces compliance. Can you find out which wilderness program it is?
Seriously though, if you can talk to him, tell him to shut his mouth, pretend to be the good son for a while longer, and arrange a ride for him on his 18th birthday. Have a couch waiting for him to let him crash on till he pulls his life back together. He's going to need to do a fair bit in terms of getting new I.D., a job, clothing, and so forth.
This could get pretty cash intensive.
Either way... PLAY THE GOOD SON... "Yes massah, No massah, You dah man Massah.. LOves dah Shortridge Massah.." but don't go over the top. A simple agreement to stay at Shortridge till he graduates will suffice.
But, on his 18th birthday, "Peace suckahs."