Styrofoam lunch trays, left, have been replaced by recycled cardboard trays at Francis Scott Key Middle School in Silver Spring, Md. Montgomery County is getting rid of Styrofoam lunch trays, opting for recycled cardboard trays instead. (Katherine Frey/The Washington Post)

Luis Pozo’s lunch tray was the size of a notebook, a thin cardboard rectangle he used to carry his noon meal through the cafeteria of Francis Scott Key Middle School in Silver Spring.

The eighth-grader loaded it with chocolate milk, potato rounds, a burger and a fruit cup. When he was done, he stacked the tray onto a growing pile.

“They can be recycled,” Luis said. “If we don’t recycle, we’re going to destroy our planet.”

It was a sign of times to come in Montgomery County, as Maryland’s largest school system leaves behind the long era of the polystyrene lunch tray for a more environmentally friendly replacement that will be used to serve up nearly 15 million school meals a year.

Starting in the fall, Montgomery expects to stock lunch lines from Clarksburg to Silver Spring with trays that are recyclable.

The change comes as schools across the region and nationwide aim to go greener and yet not overspend. Arlington replaced its foam trays with cardboard four years ago, and six urban school systems, including New York and Chicago, joined forces to leverage their buying power to get better prices on more environmentally friendly trays and healthier foods.

“We’re now seeing a revolution in cafeterias around the country ditching polystyrene and moving toward compostable trays,” said Mark Izeman, a senior attorney at the Natural Resources Defense Council. For Montgomery, he said, “this is a great move from an environmental and public health standpoint.”

For many districts, one of the biggest obstacles to scrapping polystyrene (which many refer to by the trademark “Styrofoam”) has been price.

“The conventional wisdom was they were too cheap to change,” says Eric Goldstein, chief executive officer for school support services in the New York City Department of Education. New York alone has 1.1 million students, many of them using foam trays “that go right into the landfill,” he said.

During the 2014-15 school year, Goldstein said New York and its five partner districts — the Urban School Food Alliance — will move from polystyrene to a compostable round plate with compartments.

“We’re very excited about this,” he said. “We’re already hearing from other districts that want to copy us.”

In Montgomery, Marla Caplon, director of food and nutrition services, said polystyrene goes back to the 1970s and that she’d received quotes as high as 28 cents each for cardboard trays, nearly 10 times more. But the gap began closing in recent years, she said, and the district has worked with a manufacturer to create a new product.

The new trays at Key Middle cost 4.3 cents each, which would mean a hike of about $140,000 a year. “It’s close enough to where we can stretch,” she said. The bid process for next year is underway.

At Key Middle, cardboard trays have been tried out since late April and have been welcomed. Key was a 2012 national green ribbon school, and it has a strong environmental focus.

In the din of a recent lunch hour, students filled trays with French bread pizza, baked cheese dippers, yogurt, burgers and chicken patty sandwiches.

A few students said the cardboard can be wobbly, so sometimes an apple or a milk jug will roll off the tray. Some spoke of environmental advantages.

“Even though it’s kind of a small step, I think maybe it can spread out to other schools and do something for our environment,” said Yemi Djayeola, 13.

The foam trays have been a passionate focus for students with the Young Activist Club at Piney Branch Elementary, who had campaigned and raised $10,000 to bring reusable plastic trays and a dishwasher to their school. Margot Bloch, 13, now in middle school and still a member of the club, called cardboard trays a major improvement.

“It’s a really good step to move from polystyrene to paper trays, but we would still like to see our dishwasher pilot happen,” Margot said.

Caplon said Montgomery’s polystyrene trays were not tossed into a landfill and did not go entirely to waste. They were incinerated, she said, in a process that produces energy. The cardboard trays will be recycled unless they are splattered with food; they are also compostable.

In the Washington region’s school systems, not everyone takes the same approach. In D.C. public schools, all disposable items must be reusable, recyclable, made of recycled materials or easily compostable. In Fairfax County, polystyrene lunch trays are taken to a plant in Lorton, where they are processed into electricity, said schools spokesman John Torre.

By contrast, Prince William County washes its reusable plastic trays, and Loudoun County relies on a foam tray that officials say is environmentally friendly. Prince George’s County’s lunch trays are not recyclable but are biodegradable, so they break down in a landfill, officials said.