My son also started Kindergarten at 4, and was the youngest in the class. He did fine and continued well all through his school years; went on and got a college degree. I hear from alot of parents that you shouldn't put your child in at 4, especially a boy, but my feeling was[is], try it, you can always pull out if necessary. And, yes, even my older kids were always tired at the beginning of the school year; after all those late nights in the summer! HA HA, I was tired, too! I think he will love it once he gets into the routine. Glad he is doing well and enjoy your free time!!!