I feel like your post is exactly what I've been thinking about for us. I really was considering this same situation for next year, but my son seems to want to go back to school because he has friends there now. I think it's a great idea if your child wants to do it. That way when he goes back to school, he will hopefully be a bit less ahead and can learn a reasonable amount in the next grade. My son also skipped a grade and was learning way too quickly and then would get bored, so now I keep him away from most workbooks and instead focus on violin, computer programming, and robotics. We will do these things over the summer and see what he wants to do for next year. Good luck making your choice!
