I know this is a bit trite, but I'm sending my DD13 to school to get an education, not play sports. Even though she is a quasi-sporty kid, that was not at all a consideration in either of her grade skips.
That being said, my daughter did enjoy being a ten-year-old seventh grader swimming on the middle school varsity team with mostly eighth graders. And she does a good job of keeping track of relative victories - e.g. being the top IMer on the HS JV team as a twelve-year-old is quite an accomplishment, even if she is not likely to make varsity until she's a junior.
Being competitive at sports is fun, but unless your kid is in the top 1% in ability, he'll likely be earning a living using his brain, not his athletic skill.
--S.F.
