I'll tell you our experience. My oldest started K a year early. He has a fall birthday so it wasn't all that early. It was fine. The next year we kept him in K again because we liked the K teacher and she did a great job differentiating. The following year he was in a K-1 mixed class. That was fine too but at that point he was in first grade as one of the oldest in his class. This year he started in a K-2 class (oldest in class) but then was moved after a month to a 3-8 class (youngest in class).
My take away is that you do the best you can year by year. If you think he can handle it, go for it. If it doesn't work out, you can make adjustments.
