EAST ORANGE, N.J. — Sweaty after a long, hot day spent playing in the park, more than a dozen children stopped in their tracks and jockeyed for a spot in line outside a recreation center on a recent June evening. They rubbed on hand sanitizer, then walked up to a concession stand window and grabbed a tray of food: barbecue chicken sliders, apple slices, baby carrots and a half pint of 1 percent lowfat milk.

Dinner was served.

"Are you hungry?" Brigita Asiedu, 35, asked her daughter Nhyira, 9, as she cozied up to her meal in the cool shade of the playground equipment.

This scene unfolds five days a week at parks throughout the New Jersey community of East Orange, about 20 miles west of New York City, and at almost 49,000 sites across all 50 states and Washington, D.C., where federally funded summer meal programs are available at no cost to participants.

Nhyira Appiah, right, eats her meal at Rowley Park in East Orange, N.J. She began taking part in the free meals program after her mother discovered it. Jeenah Moon / for NBC News

But for every Nhyira who gets at least one free meal a day during the summer and who might otherwise go hungry, an estimated six children who should be getting that same meal are not being fed for a variety of reasons.

Despite best efforts by officials and hunger advocacy groups, it's a problem that has worsened in most states.

In a new report released Wednesday by the Food Research and Action Center, a Washington-based nonprofit focused on eliminating poverty-related hunger, last summer was the third consecutive year in which participation in the nation's federal summer nutrition programs fell — reversing gains made from 2012 to 2015 and underscoring the difficulties of closing the widening summer meal gap.

On an average weekday in July 2018, the National School Lunch Program and the Summer Food Service Program served a combined 2.9 million children, down 5.7 percent or 171,000 children from July 2017, the report says.

Across the country, some communities — even those with meager resources and financial means — are doing what they can to ensure children aren't only eating but eating properly. In East Orange, which has one of the highest poverty rates in New Jersey and where about 70 percent of students qualify for free or reduced-price meals during the school year, sites are offering dinner for the second consecutive summer as a way to capture more participants.

The hurdles of getting additional children fed in East Orange, a compact and urban city, also differs from other places grappling with their own unique challenges.

In Humboldt County, California, a food bank known as Food for People has partnered with the county transit authority and UPS to deliver meals prepared by senior center volunteers to its 18 summer meal sites throughout the county — an area roughly three times the size of Rhode Island.

Carly Robbins, Food for People's development director, said between 500 to 600 children benefit from the arrangement in the county where 60 percent of students enrolled in county schools are eligible for free or reduced-price meals.

"We have a lot of road to cover," Robbins said, "and our total mileage just for the children's lunch program is over 500 miles" per week. She added that additional grants and donations help shoulder the costs.

The drop-off in summer meal engagement nationwide becomes clear when comparing it to the school year, when about 20 million students are fed free or reduced-price lunches across the country, according to the U.S. Department of Agriculture. For every 100 low-income children who received a school lunch in the 2017-18 school year, only 14 children received a summer lunch in July 2018, down from 15 children in July 2017.

The Food Research and Action Center's report, which analyzes USDA data, focuses on July because the months in which the school year ends and when classes return vary by each state and school district.

The issue of child hunger was highlighted earlier this year following viral stories in which students were unable to afford lunch or felt shamed over their school lunch debt.

To be clear, researchers say, the number of children participating in a summer nutrition program, whether it's lunch or dinner, isn't down during the summer because more families are able to afford food on their own — rather, children aren't able to access these free meals as easily as they would during the school year. Children may not have transportation to get to the meal sites or communities are unable to find enough sponsors or the space to host children during the summer.

"There is a cost, but we have a choice in how we spend our money in this country," said Crystal FitzSimons, a co-author of the Food Research and Action Center's annual summer nutrition status report. "It's a sad commentary on the fact that we are not providing kids what they need during the summer."

In general, summer nutrition programs are administered by each state and operated in communities where at least 50 percent of children qualify for free or reduced-price meals during the school year. School districts, local governments, faith-based organizations and nonprofits are among the sponsors, and they get reimbursed per meal by the USDA.

Any child 18 and younger can go to a site and eat at no cost. For some of them, it is the only meal they will have that day, and for others, it may be the most nutritious meal — indicative of the problem of food insecurity in the United States, advocacy groups say.