I hear you and can appreciate your perspective. We all make decisions for our children that is right for them and perhaps for us as well. For my DS, I have always felt strongly that he never get special considerations/handicaps and that he acquire the flexibility of producing the approach requested/demanded. That is why I did not request his first math acceleration until age 7 in 2nd grade. That was the point where he can clearly meet the verbalizing/writing demands of 4th grade math and be flexible/fluent enough to produce any methods requested. There was no challenge math-wise post-acceleration but DS still remembers fondly the challenge of proofing/explaining his solutions.
You are fortunate that there is a good fit between your philosophy and the school's. In our district, DS would not have been allowed to accelerate if writing was an issue as that was on the check-off list. The district doesn't want second-class citizens. I guess it comes back to concern with liability from disgruntled parents who later regret the acceleration.
