That is holding the school responsible, although I understand your reasoning.

It is the disappearance of childhood.
Latch key kids. They are told to stay indoors until a parent or older sibling comes home...which can be quite late.
Pedophiles....parents are petrified to let their kids go outside, and so an outing to the park has to penciled in.
Video games...the electronic babysitter.
DVD's....watching favorite movies OVER and OVER again, another modern day wonder that allows sedentary lifestyles create a market in and of itself.

the list goes on...the children are becoming little adults.
Outside play is becoming obsolete.

There is organized sports that is prolific among families now...but that has a price tag, that not every one can afford...including yours truly. I have time though...so I am able to take the wee one on a walk...to the park...play soccer.

There is a price/trade off for everything we do.