Like many moms with children in middle and high school, I can remember when recess and gym class were an everyday part of kids’ lives. I grew up with daily games of kickball, ultimate Frisbee or volleyball, laps around an asphalt track ringing a football field and gym clothes crammed into a locker for days at a time! But over the past couple of decades, most of that’s changed. Physical education classes — the once ubiquitous PE — have been disappearing from the nation’s schools, a victim of budget-cutting and standardized-test mania. During the summer months, many children get a fair amount...