If a child is intelligent holding them back is actually a disservice. Some kids need to be challenged. I have a child with a 4th quarter birthday and after careful consideration determined that if I held him back he would be bored in class. As a late birthday myself I could not imaging being "held back" in the 80's. I have also seen many late birthday holdbacks mature earlier but also peak to early and get frustrated once they can no longer simply bully younger kids. Eventually they all hit the ceiling.