Hi Mom2Two.
My son skipped K. I can't tell you what decision to make for your son but can tell you that we also struggled with what to do at that time for our son. He is now in 3rd grade, has individualized math instruction and is in the 5th grade book. We haven't regretted skipping K at all, ever.
Our decision was based on his unique situation - he had been in full time daycare since 12 weeks old. He had basically had two years of preschool with the last year called PreK and focusing on the exact same curriculum that they were offering at the public school K program. We were already having behavior problems in preK. His achievement testing showed that he had mastered the K curriculum 5 months BEFORE he would have even been eligible to start K. So we advocated for 1st grade early entry. We didn't get it until we had private IQ testing and out of level testing done. So, he started first grade at 5y5months old.
It sounds like you have an ideal situation to have him attend a K program now and then see what he's like come next summer. If he's ready for first then he can enroll as a first grader. If he's not ready, then you could put him in the public school at K level, since that's where he'd be anyway, if I'm reading your post correctly. Sounds win/win to me, to put him in that K program now at the private school if you can.
