if the intellectual/emotional/social fit for your child with the other kids will not work, the entire point of K being a social year is an invalid point.
If he cannot play the games the way all the others want to
If he cannot understand why they all learn so slowly (to him) and take so long to get something done
If they don't understand perfectionism (if he has this)
If they look at him strangely because he can read/write/do maths...
He will then either a) withdraw or b) act out or c) try squash himself to fit in with their perception of normal. Neither is cool for him, the teacher, the other kids or for you.
I hope you find something that works well - I quite like the idea of learning stuff at home and then school only for socials - ie, where learning cannot get in the way (largely) of having fun with other K kids.
