http://aer.sagepub.com/cgi/content/abstract/41/1/115

http://www.4children.org/news/900prek.htm

P.S.- There is a difference between a preschool and a daycare, but daycares have their benefits in school readiness as well.

So do not worry they are not trying to push calculus on your kid.

This is of course when I went, I do not know how things have changed.

I just remember coloring and learning basic shapes and stuff.

Of course if this is an Asian country you are talking about they may take this more seriously.

I recently learned that in Asian countries they have to compete just to get into the best High schools!