I picked up Malcolm Gladwell's Outliers recently, and decided to use an out of town flight to read it.
Right in the first chapter, I was hooked. Gladwell talks about the effect of being born in the first few months of a year, and the major advantages it gives people in sports.
What struck me was about school.
"Elementary and middle schools could put the January through April-born students in one class, the May through August in another class..."
I'm going to sort my students out by birthdate when I return, and see if jis supposition makes sense. I suspect there is an effect.
BTW, just to disclose, I am a March baby.