The researchers, who presented their findings at the European Congress on Obesity in Amsterdam, said students who got more exercise at school compensated by doing less at home, and those who got little gym at school made up for it by being more active at home.
Alissa Fremeaux, a biostatistician at Peninsula College of Medicine and Dentistry in Plymouth, England, and colleagues studied 206 children from three primary schools with widely different amounts of scheduled physical education.
Children attending one school got on average 9.2 hours a week of scheduled physical education; children at the second school got 2.4 hours a week and those at the third had 1.7 hours in a week.
The researchers had the students wear accelerometers, which record time, duration and intensity of activity.
The study found that although the children attending the school with many hours of physical education had 40 percent more activity during school hours than the other children, their total weekly activity was no different from the others.