That is one of the area the Iowa Acceleration Manual looks at. I answered in your other post too. If sports are a big part of your lives, I could definitely see where grade acceleration would be difficult especially if the sports were largely size driven, football, basketball etc. Now maybe swimming, tennis, golf, etc. wouldn't have such a large impact. There still would be earlier muscle development though. It's hard to say though as there are family tendencies towards earlier or later puberty. Where we lived in TX though red-shirting was so popular for boys to give them an edge on getting a starting position, accelerating there would really place them two years behind most boys in their class. Of course as you mentioned there is always community sports and I know our community has very competitive traveling sports for kids.
