My DD goes to a private Prep school. She is in 4K now and will be in 5K (just like kindergarten) in the Fall. Its run as a Christian School but is attached to a local Assembly of God church but they teach Christianity not Assembly of God.
Tuition is $4,280 per year.
There is another non-church related private Prep school in town that is MUCH more. It is about as much as college. Jr K and K is $7,500 and 1st grade is $10.5 K per year.
The cost differencial means nothing. My daughters prep school makes it in US News & Today as one of the best Prep schools in the state, while the expensive one doesn't. So ya know, its just the school and the feel you get from it. I think a private education is priceless, my daughter loves her school as do I!
Good luck with the decision!
Editing to add, I just bought 1 dress, 2 shorts, 1 skort, 1 shirt for $70.
If the school does not have specific uniforms but says "khaki pants, white shirts" then you can get a lot at Sears.com. I think you DO need 5 or more especially in the warm months because they play outside (after school) and come home smelly. Just depends on how much you like doing wash & ironing.