For students whose tests and textbooks have migrated to screens, technology as gym equipment may have been only a matter of time. At West Potomac High School in Alexandria, Virginia, students can take gym class without the gym, and on their own time. They wear fitness trackers to monitor their progress. Supporters say virtual PE keeps students active while freeing up more time for electives. It’s not clear how many schools are embracing the trend, which comes with some cautions, including the privacy of student data. And some worry that students exercising on their own may miss out on important social concepts such as teamwork.