The majority of the top players are held back. Don't laugh - many do start them late right from kindergarden, others wait before high school. One of my sons was a November baby not turning 18 till towards the end of his freshman year in college. He played high school ball against kids who graduated 2 years behind him but were less than 3 months younger than he was. It has totally changed from when I was a kid. Between that and after high school prep schools , it's why we rarely ever see 18 less 17 year old college freshman athletes. Just a sign of the times. In retrospect , I probably should have waited to start him but never even thought of it.