Nothing seemed special about the plates from which students at a handful of Miami schools devoured their meals for a few weeks last year – round, rigid and colorless, with four compartments for food and a fifth in the center for a carton of milk.

Looks, however, can be deceiving: They were the vanguard of what could become an environmental revolution in schools across the United States.

With any uneaten food, the plates, made from sugar cane, can be thrown away and turned into a product prized by gardeners and farmers everywhere: compost. If all goes as planned, compostable plates will replace plastic foam lunch trays by September, not just for the 345,000 students in the Miami-Dade County school system, but also for more than 2.6 million others nationwide.

That would be some 271 million plates a year, replacing enough foam trays to create a stack of plastic several hundred miles tall.

“I want our money and resources for food going into children, not in garbage going to the landfill,” said Penny Parham, the Miami school district’s administrative director of food and nutrition.

Compostable plates are but the first initiative on the environmental checklist of the Urban School Food Alliance, a pioneering attempt by six big-city school systems to create new markets for sustainable food and lunchroom supplies.

The alliance members – the public school systems in Chicago, Dallas, Los Angeles, Miami, New York and Orlando, Fla. – are betting that by combining their purchasing power, they can persuade suppliers to create and sell healthier and more environmental-friendly products at prices no system could negotiate alone.

“We pay about 4 cents for a foam tray, and compostable trays are about 15 cents – but volume is always the game changer,” said Leslie Fowler, the director of nutrition support services for the Chicago school system. “We want to set the tone for the marketplace, rather than having the marketplace tell us what’s available.”

The alliance’s next target is healthier food. It is already looking at potential suppliers of antibiotic-free chicken. School officials say possible future initiatives include sustainable tableware, pesticide-free fruit and goods with less packaging waste.

If the alliance succeeds, it could help change nutrition and sustainability policies across the nation. Already, other school districts are asking to join the group.