This may sound harsh, but for every adult that people can actually name as being 'harmed' by acceleration, I can name 2 adults who were redshirted for athletics and their world fell apart when they realized that high school athletics was the best it would ever be for them.
We did not hold him back because of college scholarship. Sports at his age is very important socially. We did not do this for scholarship. He was initially held back for maturity, not to stand out as the best. I would like him to feel more average is some ways. I'm not to worried about his world falling apart by sports maxing out in HS. I think it great he is hanging with the better team mates and that gives him confidence and freindships.