One sure way to get parents exercised is to take away recess, the playful part of the school day when their kids can run wild. In some places, it no longer exists.

The proportion of schools that don't have recess ranges from 7 percent for first and second grades to 13 percent by sixth grade, new government figures show.

Put in perspective, the overwhelming majority of elementary schools still offer recess each day, usually for about 25 minutes. Most children get one recess a day, if not two or three.

What troubles parents, though, is a sense that recess is under siege, so much that the Cartoon Network and the National PTA have launched a "Rescuing Recess" campaign. Kids are leading the huge letter-writing effort to school officials with one theme: Let us play.

"The reason I get riled up — and that most parents do — is we see recess as an opportunity for children to play," said Diane Larson, a mother of four in Tacoma, Wash. "It's a time for children to be imaginative, to show innovation on the playground. And it's one of the times when kids actually get to interact with their friends."

Larson and other parents in her district want elementary schools to offer separate recess periods each day, but students often get only their lunch periods to let loose. The recess drop-off is most noticeable in third grade, she said, when preparation for testing kicks in.

Where recess is in decline, school leaders usually blame academic pressures. Under federal law, schools must test and show progress in reading and math starting in third grade.

But how schools manage their time is a local decision. Recess competes with many other activities for schedule time, from music and arts to gym classes and computer classes.

At Rivers Edge Elementary outside Richmond, Va., children get only one gym class a week, which makes their daily recess period even more important, said PTA President Wendy Logan.

"The kids study all day, and they need some time for social activities," Logan said. "And those kids who struggle sitting the whole day — they're the ones who need it the most."

Nationwide, 99 percent of elementary schools schedule time for physical education apart from recess. More than half, though, offer those gym classes only once or twice a week.

Elementary schools in poor communities offer less recess, and less overall time for exercise during the school week, than other schools, the government study found.

The 2005 school figures, released Tuesday, come from the Education Department's first study on food and exercise in public elementary schools. It includes no data from previous years to determine, for example, whether recess has been declining over time.

Local disputes over the elimination of recess have popped up in Atlanta, Boston, Chicago, Miami and other communities. Such local stories, not the national picture, worry parents.

To them, recess is an institution — how could an elementary school not have it? When are kids supposed to yell with their friends, play tag or kickball, just have some fun?

"It's how I believe they start building their social structure," said Sandi Hocker, a mother of two in San Antonio, Texas. "Their P.E. classes are organized, and they are activity related. I think (children) need recess just for the socialization."

In an informal survey by the National PTA of its state leaders, more than half said daily recess is at risk. Only 9 percent were confident recess would not be reduced in their school.

The Cartoon Network has pledged more than $1.3 million to save recess. That includes more than $300,000 in grants to PTA chapters for participating in the ongoing letter campaign.

Mark Schneider, commissioner of the National Center of Education Statistics, presented the government findings on recess and exercise. He declined to draw conclusions from them.

But given the obesity rates among children, he said: "I think we should all be concerned about any schools that aren't providing sufficient physical activities."