Gladwell's discussion of birth dates and hockey don't have relevance to academic acceleration. Most sports are by age until high school, at least what I've seen. If sports is a serious pursuit than yes, bigger, stronger, faster, older may be a deterrent to acceleration. But I thought Gladwell was purely pointing out the "outlier" of birthdate as one unlikely factor of success in hockey (the typical factors considered are coach, how many yrs played, etc.).