Have you considered non-profit preschools such as FUMP (First United Methodist Preschools). They are generally affordable and run on a national cirrculum. Yes they are christian based but offer a loving and encouraging environment for children to learn. And most of them even offer scholarships. From experience, they offer 3 day to 5 day half day programs. This generally depends on your location and the need in your community. Good luck in your search.