What do you think about partial homeschooling for the rest of the year...I'm thinking about keeping him out on Tuesdays and Thursdays. Would the school 'go for it?' Or even early pick ups on those days? Can you invent music lessons or some other kind of issue that nescessitates him to be let out early 2 days a week? Perhaps trump up SAT tutoring 2 x/week so he can take the SAT or ACT next year when he is 11? What about getting him involved in acting that might be a good pretext for missing a lot of school? (Not everyone's cup of tea, but it worked for Ruf.)
That might be a way to encourage him to let the homeschooling start early.
I wish I had a resource in Southern Cal. I wonder if you called Davidson YSP if they know of any - you are sort of 'close by.' Have you contacted the state gifted association?
Love and More Love,
Grinity