I agree with all the comments above, I just was having trouble articulating all of them so I waited for someone else to answer. DD8,DD4 were in "school" because both DH and I work. First private and now DD8 is in public. Both kids are very happy. I'm disappointed in the challenge at public but that's some of our doing, DD8 doesn't mind it being easy more time to socialize (she is honest about how easy it is to me but doesn't tell her teachers).

One thing I would add is maybe he could do a private kinder (if it would be a better fit) if he's 4 vs preK. Depending on your district if you wait long enough you could enter them in public with an effective early entrance. For example, in our district once you attempt to enroll them in 2nd grade or above, they look at report cards, test scores not age. For K,1 they are strict on age limits. I only say this because our montessori is wanting to put DD4 (march bday) in Kinder next year. We will probably do it and deal with other decisions later.