I know you’re talking about preK/4 year old but think about subsequent years too. We did the opposite, our son was a few days from the cut off and should have gone to K this year but we kept him back to mature more. For him if was definitely the right move so - the only reason I can think of to push it on the other side is if you can’t easily afford another year of care before public school (and that’s a completely valid and legitimate concern).

But K is hard now, it’s real work, hardly any play. I had to put my money where my mouth was but I wanted to give our little guy another year of being a little kid before he goes into the meat grinder.

So think about your kid’s level of social/emotional/academic maturity. If he excels in all, talk to the school district. Otherwise I’d embrace having another year of fun school before things get real.