To up-date our situation:

Early entrance was not enough and ds did not enjoy the curriculum through 5th grade. Additionally, he has not really found any peers in his class even among the smarter kids although he does enjoy talking with the smartest kids two grades up (21/2- 3 years older).
He has also encountered hostility from a few teachers and been told by one of the kinder teachers that he should not seek math subject acceleration (despite being offered to skip 6th, then offered to skip directly to high school from 6th).

If he had been offered to skip 2nd, 3rd or 4th grade, he may have found a niche.

Since the administrators at our present school could not give assurance for continued math acceleration to Alg1 in 7th grade, as explained to him by an administrator that he is a minority and they had to concern themselves with the needs of the majority first, he will attend another private school next year. This one is expensive, but we received a considerable financial aid/scholarship award and they have also made arrangements for him to take Alg1 with older students.