I think that the most important thing is that math is taught from a Constructivist perspective.

http://teachingmybabytoread.blog.com/math/

We are using Right Start to afterschool my six year old. Right now he is doing Level D, but here is my review of Level C:

http://teachingmybabytoread.blog.com/2011/06/14/review-right-start-level-c/