Thanks to both of you for the responses so far. It is a lonely world out here!
The school is going through growing pains, we otherwise like the school and the teachers we met. But we want to see where they end up in say two years time, because if for some reason they don't survive (we might be just too paranoid/pessimistic here), we will end up with no private school, and I might have to leave my job to homeschool him, which I don't plan to do yet.
We are a bit apprehensive about telling the non-GT school that accepted us that our son is highly gifted, because we are afraid of stirring the pot and ending up with no school. This school is very well respected, and apart from the no vertical differentiation issue, it is a darling school that fits our family philosophy for education.
So I am guessing my base case for the next two years, is to work with the school and see what problems we get (or not) but that again doesn't allay our concern that he might not get to show his real abilities. Also our son's scores are more "normally gifted" in areas other than VSI, so they might be a good fit in other areas, just not in math. I am also assuming it is much easier to support differentiation in reading as it doesn't require 1:1. I may be able to hire a math tutor or tutor him myself at home if we want to test his math abilities, but I am apprehensive that he might then further diverge from his peers in math and get bored at school.
He has not received any formal instruction on math and reading both at home and school, our pre-K focuses on kindergarten readiness and social skills. But as a result we have not tested where he'd be in math. All we know is that he is a crazy lego guy, with design complexity years ahead of his age. We have read nurture shock also, and we are thus apprehensive about interpreting test results as high giftedness before we test his real limits in formal math instruction; though our psychologist told us that at this score level, the giftedness is real as the barrier to get that kind of score is very high. Also there is an incidence of high giftedness in our family.
