Here is the Denver Preschool Program. Basically, they rate the quality of each partner preschool and offer “tuition support” of up to $365/month, depending on family income, to help families send their kids You can go here to see the tuition support calculator.
They didn’t have to establish new programs. What they did do is establish quality standards and incent higher quality by paying more tuition support if parents attended higher quality schools. Pretty powerful.