Grace Brown's schedule at West Potomac High School in northern Virginia is filled with all the usual academics, and she's packed in Latin, chorus and piano as extras.

What she can't cram into the 8:10 a.m. - 2:55 p.m. school day is gym class.

So she's taking that one minus the gym, and on her own time.

The 14-year-old freshman is getting school credit for virtual physical education, a concept that, as strange as it may sound, is being helped along by availability of wearable fitness trackers.

For students whose tests and textbooks have migrated to screens, technology as gym equipment may have...