Soooo, my son went to a Montessori school for pre-k and K. Pretty good group of kids and parents. There were some summer birthdays including late august. The school convinced a few of these parents that their kids were so smart they needed to be skipped ahead a grade. Can't remember if they skipped K or 1st, but they skipped. So a couple parents tried to move over to public school and the district told them they don't let kids advance until after 3rd. Low and behold wouldn't you know it, the families were locked into another 2 years at the Montessori school. Now that the kids are in HS, the parents are pissed. Their kids are not able to really compete at sports with kids in their grade levels who are 2-3 years ahead.
My son is a May bday, so he's already young. Thank God my wife listened to me when I argued to leave him on grade level.