What a hard situation you have. I agree that getting him out of that environment and homeschooling would be good for him. I take it he disagrees? What state are you in? My advice would be to start with
Home School Legal Defense. ..Search the net to see if you have a local homeschool support group.
Here are a few other links that may help you
Homeschooling Today
Homeschooling 101
Why Homeschool?
I'll add you to our "ping" list and ask other families for their 2 cents.