On Friday afternoons, a low rumble fills the halls of Parr's Ridge Elementary.
The source: large gray trash bins, rolled by a squad of second-graders and parents at the Mount Airy school.
The green letters and circle of arrows on their white aprons state their purpose. They are the Green Team, the school's recycling crew, which collects scores of pounds of paper - construction, copy, notebook - each week.
Launched last fall, the team has mushroomed from an effort to ensure "we recycle" became a schoolwide practice to one that aims to spread such thinking throughout the district.
"It's been a great start," said Erin Tunkel, the Parr's Ridge mother who, with second-grade son Ryan, 7, developed the concept. "We need to stop being such heavy consumers. We need to just be aware of what we're buying ... and what we're throwing away."
Children can help make those small changes, Tunkel said, by talking to their parents and encouraging them to modify habits, once they learn the realities of "the dump" - where trash goes, but doesn't necessarily go away.
Such thinking echoes that of county officials, who have spent recent months talking trash, and the best way to dispose of it. Many have emphasized the need to ramp up the recycling rate of about 30 percent - something a recently approved recycling manager position is meant to help jump-start.
But throughout the debate, there has been an emphasis on the importance of education - and targeting the young.
"Recycling is something that needs to be repeated," said J. Michael Evans, Carroll's public works director. Schoolchildren are "the best repeaters," he added, "because they come home enthusiastic about something, and they show Mom and Dad how to do it, and they sort of police it."
The school system has been recycling paper and cardboard for a while, said Raymond Prokop, director of facilities. More recently, with the county's introduction of single-stream recycling, that has expanded to other items, he said.
"There seems to be quite a bit of interest out in the schools," Prokop said, adding that kids, in particular, appear to be driving the enthusiasm. "We encourage it."
The Green Team is about "moving out of the conversation into action," said Teresa Shattuck, a parent at Mount Airy Elementary, who helped start that school's effort in March. At that school, fifth-graders troop through the halls each week, collecting paper and bottles.
