Personally I think that one's real education begins until middle school.
Kindergarden is mostly social and motor skills
Elementary is mostly social and basic skills (mainly math, music, reading and writing)
Middle School though, is where their education 'gets serious'.
Why pay for private schools before middle school is something I do not understand. If your kids cant read,write,add,subtract and do basic 2-digit multiplication and division before they are 10 then something is clearly wrong with the parents and the school itself (but mainly the parents IMO. Sending a kid to school is not an excuse for not being involved in their education).
So... send them to public school and save that cash for their college I say