The target is 3k people. 20% in k-12 is what I roughly expect for this sort of community.
I went to a few K-12s with fewer than 400 people. They were great.
American public schools are notoriously inefficient. Spending tons of property tax revenue is not necessary, just politically challenging to undo. You might be able to pull it off in a project like this. Or just say there are no public schools and outsource education to parochial schools or something. It doesn’t really matter - education has minimal impact on life outcomes until high school/college. It would not be my first concern with this kind of experiment.