I have a 15 year old girl cousin, who just was too out of control.
They sent her here:
http://www.vpp.com/teenhelp/scl.html
She doesn't get to return for a year. They actually had to keep it a secret and arrange for her to get kidnapped to get her there, so she wouldn't run away when she found out. She was dabbling drugs among other things, but mostly behavior issues.
I was legal guardian for my 15 year old sister (at the time) for two years once, it was hell. Teenagers are wicked. Years later both my sister and girl cousin have confessed to doing things in my house I would have strangled them for.
Good luck with the kid. I wouldn't want to be a teenager again for anything.