Strenuous physical activity not only improves health, but also builds character.
Mandatory physical education for all K-12 students in the United States. At least an hour every day.
How about forbidding parking at school, and promoting students travelling by bike?
This is unreasonable in much of the United States; moreover, there are plenty of parents who would not be amenable to their children traveling to school alone.
Oh, I understand, we are only talking indoor sports here. Wouldn't it be quite costly to build the many sport halls required if physical education in school is to be extended?
Surprisingly maybe not...
Most Europeans would be disgusted to see how much sports-related infrastructure is already in place in many American high schools. Many high schools, especially the larger suburban ones, have stadiums, gyms, and training centers that would rival a lot of smaller colleges.
Additionally, many smaller schools may utilize corporate sponsorship to pay for sports-related infrastructure.