Im sorry I wish I could help with the legal issues with some advice but I cant.
I did want to post some advice as someone not far from your sons age with AS on the subject though.
Im 20 and I have AS I also went to private schools from 7-9th grade, I then went to public school and ended up skipping almost every day. The next year I went back to a new private school, was there for two years and ended up home schooling the last year and a half or so(I graduated early despite the problems).
Private schools/home schooling are a great way often better to get an education especially for children with special needs. But there is a downside in that the interaction with other people a person gets also goes down. People with AS already struggle in dealing with other people and 17 is an important age for interaction.
When I went to the second private school it was smaller and then home schooling it was just me, this caused me to further become reclusive and developed into serious problems.
If your going to put your son in private schools and especially while he is currently sitting at home find other activities for his time that envolve other people.
It doesnt need to be all the time God only knows I would have snapped if I was forced to be around people constantly. Also make sure they are things they are intreasted in regardless of what it may be music, video games,(my personal pleasure)art whatever so he doesnt resist going as much.
As I said I had a lack of interaction with other people and I just went more and more inward and now I have serious problems dealing with other people. If I would have gotten out and went to the comic book store and played cards or talked games with my fellow geeks im sure that my problems wouldnt be NEARLY as bad as they are nowdays. But since I wasnt working I couldnt afford to do it so all I did was sit at home.
Good luck with your sons schooling but dont forget interaction with others is very important too especially for someone with AS.