Wonder if you could draw a link between the fee differences, and the success of their first graders

Fees funding that success, parents attracted to that success also helping justify the higher prices, believing, often incorrectly, that there is a link between between the levels...then, as above, attracting the better kids means you're more likely to win games, and winning can easily be mistaken for development of course.

(I admit, it's why I chose our first SAP club...thinking 1st grade success meant developmental success along the chain)