[vecinu]

This is exactly what Malcom Gladwell talks about in Outliers: The Story of Success. He starts off by mentioning how hockey players have this age advantage since they are more physically mature than people born in other months and cut off by our artificially created system.

[dasil003]

Makes sense for hockey players given the investment they need in development from a young age and how that investment is directly based on physical evaluation. For CEOs that pattern doesn't exist save perhaps in the mind of status-obsessed parents.

[ABCLAW]

If you're the oldest individual in your elementary class, you've got ~11 months more development than your worst-off competitors. You carry that age advantage throughout every level of education you go through, allowing you differential access to awards, accolades, special opportunities, etc.

When development evens out following full development, you're already past the majority of the educational sorting mechanism - you've been scoring higher and formed by your experiences as a high performing student throughout.

[dasil003]

But in athletics you stop getting training and don't go to the next level if your performance is sub-par, so the effect is magnified.