I was never successful with advocacy. I hope the others will guide you with the voice you need.
That said, you mentioned BA as an excellent program for your son. The upper levels, Art of Problem Solving, are accredited. Try to see if they will accept AoPS. He can do the class at home, then work on the problems during "regular" math time. Any questsions, AoPS provides support. The only school support he would need would revolve around technology. Pre-Alg would be a great starting point as it does a wonderful review prior math concepts.
JH CTY is also accredited and I made sure the school knows that. They are saying no. The reason I picked JH CTY is because there is an instructor available rather than relying on a completely self-taught instruction via workbooks. It's SO expensive though. Ugh.
