I am a stepmom. My husband's ex was incredibly difficult. We didn't even try discussing alternative, quality education with her so the kids went to her crummy neighborhood school.
One of the pieces of advice I have to give parents of divorce is to do the best you can to find the path that you agree on. Obviously that's a difficult thing to do or you would still be together.
So, my recommendations is you find a path that you both can agree on.
First, is he open to homeschooling? If not, would he agree to a Sudbury Style School http://www.psychologytoday.com/blog/...sudbury-valley
or maybe a Reggio Emelia school http://www.education.com/magazine/ar...Reggio_Emilia/
(I don't know if they go beyond preschool.)
If he is open to homeschooling but not unschooling, you could go with some of the looser curriculums. We use the www.sonlight.com
list (we use the secular books.) Or another living books curriculum. Or maybe these learning guides would be satisfactory to him: http://www.fun-books.com/books/livin...ing_guides.htm
My experience with court is that it's a huge game. Whoever has the nastiest attorney and the paid experts wins. In our area it has gotten better and they now pretty much just do a 50/50 visitation split (which I think is best for most kids, despite what each parent may say about the other parent.) However, judges want it simple and they're probably not into a lot of experimentation when it comes to school. If you and your ex can come to an agreement, that is what the courts will go with. If you can't, then it may well be who has the best attorney that "wins."