Buried in the fine print of D.C. school budget documents last spring was a detail that many parents didn’t notice until last week, when their children headed back to class and discovered that recess had been cut to 15 minutes a day.

The recess change at some of the city’s traditional elementary schools prompted an immediate protest from parents, who argued that children need more exercise to be healthy and focused in class.

That backlash spurred officials to issue guidance for schools, raising the minimum to 20 minutes and emphasizing that principals may add more time if they wish. But parents say 20 minutes is still too little, given the time it takes kids to travel to and from the playground.

“They’re kids. They need time to recharge their batteries and get their wiggles out,” said Becky Levin, a parent of a 6-year-old at Capitol Hill Montessori at Logan. “This just doesn’t really seem to make sense on any level.”

Across the country, recess has become one flash point in a debate about whether schools — under pressure to demonstrate gains on math and reading tests in the era of the No Child Left Behind law — are siphoning too much time from art, civics education, play and other important pursuits.

Recess advocates point to research showing that physical activity can have a positive impact on student achievement and emotional well-being, and is a key to addressing the epidemic of childhood obesity.

Approaches to recess vary across the Washington region. Montgomery County schools do not have a minimum requirement, but elementary schools tend to offer a half-hour recess, officials said. Loudoun County expects schools to offer 15 minutes daily.

Fairfax County also has no policy but recommends 20 minutes per day. And Arlington County schools require between 100 and 125 minutes per week — between 20 and 25 minutes per day — for children in grades one through five. Recess for kindergartners is a few minutes longer.

Recess time varies in the District. Some schools saw a reduction this year as Schools Chancellor Kaya Henderson implemented new requirements meant to ensure that all elementary students get a minimum amount of time in each subject each day: two hours of literacy, 90 minutes of math, and 45 minutes of science or social studies. An additional 45 minutes is required for an elective, such as art, music or physical education.

Henderson’s new requirements also included a minimum of 15 minutes for recess — five minutes less than the minimum specified in the school system’s wellness policy.

When parents raised questions about the discrepancy last week, officials said they would clarify for principals that the minimum expectation is 20 minutes.

“DCPS believes strongly that along with strong academics, students need access to physical activity, before, during and after school,” D.C. schools spokeswoman Melissa Salmanowitz said in an e-mail.

Under the new requirements, schools have 45 flexible minutes they may use for whatever they deem most important. Some have used it to expand recess past the minimum; others have not.

Laura Marks said back-to-school schedules showed that her daughter, a first-grader at School Within School, would get 45 minutes for recess and a bathroom break, while her son, who is a third-grader at Watkins Elementary, would get only 15 minutes to play — down from a half-hour last year.

“It makes me wonder whether anyone making these schedules has met any actual children,” said Marks, who added that her son “is going to be chewing on the rug” if he does not have more time to run around and burn some energy during the day.

Watkins Principal Dawn Clemens said she understands the concern. Watkins offers an exercise program before school and a running club during lunch, she said, as well as “brain breaks” that get kids up and moving during class.

But it’s impossible to fit everything that parents and teachers want — and everything students need — into the 61 / 2-hour school day, she said. A new science program takes up 45 minutes of the day, she said, and “Responsive Classroom,” an approach to building a positive school climate, takes 35 minutes. With those programs and the new scheduling requirements, 15 minutes was all she said she could find for recess.

“We do need more time if we’re going to do right by kids,” Clemens said.

In the aftermath of last week’s reaction, she plans to expand recess back to 25 minutes or a half-hour, and she’s puzzling over the schedule to figure out where the time will come from.

The new scheduling requirements appeared in the D.C. schools budget documents published in the spring. But the change was not communicated directly to parents, said Marks, who serves on the school system’s health and wellness advisory committee. She said she learned that her son’s recess had been cut when he came home the first day of school.

“If you want parents to be engaged, you have to collaborate with parents and not blindside them with this kind of stuff,” she said.

Clemens said she had been following the new requirements and hadn’t expected such strong feelings.

The parent e-mail group list at Tyler Elementary also was abuzz last week in opposition to the city’s 15-minute recess minimum. But at least one father at the school said he had no problem with the change.

“Physical education and out-of-school-time physical activities are things that are important to me,” Steve Sweeney said in an e-mail. “Unstructured, midday, free time supervised by adults trained as educators is less important to me. Teachers should be teaching. Students should be learning.”

Federal health guidelines recommend that children get 60 minutes of exercise each day.

The D.C. school system requires, in addition to recess, that elementary schools offer students at least 45 minutes of physical education each week. The D.C. Healthy Schools Act requires elementary schools to offer at least 150 minutes of physical education per week starting in the fall of 2014.

“Kids need to have a physical kind of break,” said D.C. Council member Mary M. Cheh (D-Ward 3), who pushed for the law. “I hope that whatever they’re doing with recess, they’re being thoughtful about how kids learn and what their attention span is, and what would make them learn better.”