Education officials yesterday urged primary schools to let children run free during recess and not keep them indoors to prevent potentially costly playground accidents.

The request came after an online survey of parents revealed 70 percent of respondents claimed their children were not allowed to play outside during breaks, officials said.

"Teachers should understand that children are born to be active, so education shouldn't run against the laws of nature," said Yang Yongming, director of the Shanghai Education Commission's youth protection division.

Officials said the commission would start an investigation into whether any schools had contravened education regulations.

In the survey on ww123.net, a forum and bulletin board for parents, nearly 140 out of the 200 people who responded said their children were told not to leave the classroom - except to go to the toilet - during breaks.

Some schools only allowed students in the corridors during the 10-minute breaks, the survey said, while others even made students do homework.

"It seems the playground is just a token offering that children don't have the right to play in," said one of the parents who identified himself in the survey as Niuniuba.

Officials from schools highlighted by parents in the survey were not immediately available for interview, but Yang said restrictions might have been placed on kids because of safety concerns.

"Head teachers are facing a lot of responsibility over campus safety, because they would be liable to pay a lot of compensation if an accident took place in their playgrounds," Yang said.

He added some schools had canceled activities after children were injured during breaks.

Some parents backed playground restrictions.

"Frenzied games during breaks will make children too excited to concentrate on their classes," said Ren Xiao, whose son goes to a school in Zhabei District. "It's not bad to prepare them better for the next class."