[JGarrick]

I just read a book that had a chapter that discussed this in relation to professional athletes. It turns out that in many sports, people that make it to the pro ranks are disproportionately represented by those who were born in the two or three months after the cutoff dates for entering youth programs as kids. That makes them nearly a year older when they start, and they tend to excel because of the extra maturity. Siince they excel, they're also more likely to make All Star teams, or to be drafted by top coaches, etc., so they get better coaching and training, and advance faster than their peers. This advantage continues throughout their youth, with advantage leading to success leading to still more advantage and still greater success.

There's absolutely no reason to think that this wouldn't also apply in school. Nearly a year older, she'll do better in school, and will likely be treated a bit better by her teachers because of her stronger academic skills and greater emotional maturity.