R.J.
I agree with Jennifer...let him fail.
Basically you have 2 choices: Prop him up for highschool, and then let him blow a whole quarter/semester at college ($ Ouch!!$) figuring it out, or let him figure it out now.
Let him oversleep, and have to catch the metro or walk or miss school. DO NOT write a note excusing it. Let him absolutely tank for a quarter grade wise. Let him know you're going to do this, and why, and stick to it.
If the school calls, be more than willing to conference. And here's you line: "We're teaching him to take responsibility now, while he's at home, rather then waiting until he's left home and then crossing our fingers. Anything that you set up with him, needs to be with HIM. We're extremely interested, and would like to be kept appraised, but these are lessons HE needs to learn. Better repeat the 10th grade, and then ace 11th & 12th on his own merits, than for us to. We've already been to highschool. He's SO capable of doing this, we're not going to cheat him by doing it for him."
I also have to second having a list of SPECIFC chores and expectations that get checked off daily in exchange for sports/friends/what have you. That way you've put the ball firmly in his court, again.
There's also something cool that can be done with teenagers. That's the Overnight Planning Trip. That's where you get to have one-on-one time talking about dreams, researching paths, & pre-reqs FOR those paths. Highschool is very very very ethereal. Use that overnight to take the vagueness out of it and start achieving/working for those dreams and goals we all have. These days, all you HAVE to have is internet access. 10 years ago you had to do a lot more planning in advance...getting course catalogues, trade & tech school catalogues, the big book of internships, and you could STILL end up on the phone trying to figure out if there's a way to rob banks for a living that's legal. (There IS btw). Nowadays nearly EVERYTHING is online...and you don't have to horrify the switchboard operators at KEY & BOA & Wells Fargo.
Best of luck to all of you!