BALTIMORE — More than 200 volunteers recently gave up their Saturday to labor in a Southwest Baltimore schoolyard constructing a modern playground they hope will promote play — and level the playing field.

Those behind the effort believe schools with many low-income black students, such as North Bend Elementary/Middle School, have been shortchanged for years when it comes to monkey bars, climbing walls and swings, and the known health benefits of playgrounds. They are making a concerted effort to correct that.

The goal has long been “to make sure every kid has access to a safe, great play space,” said AJ Pearlman, director of city partnerships for Kaboom, a nonprofit that has helped build 3,100 playgrounds in schools and parks across the country, including about 40 in Baltimore since 2001.

“Racial equity is a big part of what we’re trying to achieve,” Pearlman said. “Historically, poor black neighborhoods have been denied.”

In the past, the group has put its playgrounds in places where people have asked for them. Now, the organization is pausing construction in Baltimore to do an equity study to ensure it is putting the new playgrounds where they are needed most rather than just in places that apply. It is also focusing its effort on schools.

This is first time Kaboom has done such a study. Pearlman says it extends the group’s mission to aid cities’ most neglected corners, and it moves Baltimore toward other U.S. cities in tackling racial equity in recreation.

Kaboom hopes to complete the equity study by spring and to restart work building playgrounds at schools it identifies as most needing them, said Pearlman, former chief of staff for the Department of Health and Human Services’ civil rights office in the Obama administration.

The effort comes as several nonprofits and city agencies have taken steps to expand recreational opportunities in Baltimore, such as the move by Mayor Bernard C. “Jack” Young (D) to open city rec centers on Saturdays.

The still-nascent national trend in considering disparities in play began about 15 to 20 years ago, said Julie Nelson, co-director of the Government Alliance on Race and Equity, a national network of about 175 governments and others focused on racial issues.

She said movements in cities such as Minneapolis, Seattle and Portland, Ore., have grown from government workers’ concerns about the legacy of past discriminatory practices. Officials in those cities began considering racial and economic data when planning for social services and parks and recreation.

Officials started asking not only where ballfields were located, for example, but also why some people weren’t using them and how to be more inclusive. They examined after-school programs and other community resources, and they asked residents about barriers, including costs, distance and timing of activities.

“Over the years, more and more local jurisdictions have joined in,” Nelson said. “They’re recognizing the history of the United States, which has worked to the disadvantage of people of color. They’re recognizing that we need to be accountable today for the decisions from the past.”

Play spaces are of particular concern amid growing evidence of their importance in child development, Kaboom officials said. Baltimore’s staggering health disparities also make playgrounds an important focus; health officials often point to the 20-year gap in life expectancy between poor, mostly black neighborhoods and wealthier, mostly white ones.

The barrier to creating more recreational opportunities is now more a lack of resources than a lack of will, said Maria Brown, president of the American Academy of Pediatrics’ Maryland chapter and founding chairwoman of the Children and Nature Task Force.

She and others began a program in Baltimore almost a decade ago called Docs in the Park to promote outdoor time for kids in disadvantaged neighborhoods.

Brown said the program sprang from concerns about health. Studies show physical activity staves off obesity, diabetes and related diseases. Federal data also shows African Americans and children from low-income families were more likely to be overweight.

There’s also evidence of other benefits such as higher test scores in children, probably because they are better able to focus in class after exercising, she said. Studies also suggest play time lowers stress and contributes to social development, relationship-building and problem-solving skills.

“We refer to play as the work of children,” Brown said.

Maria Trent, a pediatrics professor at Johns Hopkins University, recently wrote the pediatrics group’s policy related to racism and child health. She said the measure was needed because doctors and community leaders need to be prepared to fix past inequities and to address ongoing incidents of racism.

Access to play time or organized sports for schoolchildren of all ages can have a big role in cities such as Baltimore that have “complicated civil rights history around access to public pools and spaces due to racial divisions,” Trent said.

She said that role extends beyond the research-proven physical benefits and stress relief.

“In a city where young people are facing so much toxic stress, reimagining play in Baltimore is an important first step in promoting health,” she said. “Creating safe and clean places . . . will also say to people who have been disenfranchised, ‘I value you.’ ”

Tisha Edwards, director of the Mayor’s Office of Children and Family Success in Baltimore, acknowledged that the city has many “play deserts,” including some at its 170 schools.

Edwards hopes the gaps can be filled by outside groups such as Kaboom, which relies on corporate donations and volunteers, as well as city grant funding. Kaboom was the largest recipient in the first round of funding from the Baltimore Children and Youth Fund, a $12 million set-aside from property taxes for youth programs. It won $500,000 last year.

One of its playgrounds costs $125,000 to $150,000, Kaboom reports.

“We need to make sure children have everything they need to achieve their potential,” said Edwards, who volunteered to help build the North Bend playground along with other city and school officials.

About 94 percent of North Bend’s 463 students are black, and, as in most Baltimore schools, the majority are from low-income families. Its playground had become run-down and, in some places, unsafe, said Patricia Burrell, principal at North Bend, which applied to Kaboom’s program three years ago.

Burrell said the school’s new playground incorporates ideas from students to heighten its appeal. The school also got an outdoor classroom, picnic benches, recycling bins and other amenities.

“This is an equity issue, especially for children of color who don’t have everyday places to play and be safe and enjoy the city they live in,” Burrell said.

The project drew volunteers from inside and outside the school community to assemble the equipment, including Lynda Jacques and Janasha Jackson, the parents of fourth-graders.

They said they expect their children to be more focused after recess. They said they may see improved social skills and a heightened level of community pride and respect for property.

“This will bring joy to the kids,” Jacques said.