(NEW YORK) -- The wheels on new school buses around the country go round and round, but they're practically the only things making noise.
School districts in every state are beginning to roll out electric buses to transport children to and from school, with a big financial boost from the federal government.
The vehicles are better for the environment and children's health, research has shown. They're quieter, too -- and devoid of the black smoke and diesel fumes long synonymous with the nearly 500,000 buses that shuttle 25 million American children to and from school every day.
$5 billion for thousands of buses
As part of a new program funded by the 2021 bipartisan infrastructure law championed by President Joe Biden, the Environmental Protection Agency will award $5 billion over five years to school districts nationwide to help them transition to environmentally cleaner vehicles, primarily those powered by electric engines.
In the first round of funding in 2022, the EPA awarded $948.8 million to 403 districts in all 50 states as well as Washington, D.C., and several territories and tribes.
The agency, which prioritized low-income, rural and tribal communities, said that money will pay for 2,571 zero- or low-emissions buses, including 2,446 powered by electricity, 109 by propane and 16 by compressed natural gas.
Students push for change in Maryland
The shift is already on display in suburban Maryland, where the public school system in Montgomery County has started transitioning its fleet of more than 1,400 buses -- one of the largest in the nation -- to become fully electric in the next 10 years.
In 2021, the district, just outside Washington, placed the largest order for electric buses by any school district: 326 vehicles, which it plans to roll out through 2024. By the end of last year, it had 86 in its fleet.
The superintendent, Dr. Monifa McKnight, told ABC News that the students riding the buses had been the biggest proponents of switching.
"Our students would come and testify at board meetings and really push us to reflect on how we were improving our carbon footprint," McKnight said. "Our county, Montgomery County, has a climate action plan that is very progressive, and the school system should be a part of that."
Switching to electric-powered buses will help the system achieve its goal of reducing its greenhouse gas emissions by 80% by 2027 and by 100% by 2035, McKnight said.
In pushing for more zero-emissions vehicles, advocates point to not just the environmental and climate gains but the health benefits as well.
Children, whose lungs are still developing, are particularly vulnerable to the fumes from diesel exhaust, according to the EPA.
Studies in recent years have shown that when children are exposed to less diesel emissions, their lungs function better, they are absent from school less and they have slightly higher test scores.
"When we remove these diesel emissions, we see the health implications, but we're also reducing the exacerbation that we see from transportation on climate change and global warming," EPA Administrator Michael Regan told ABC News.
'A real awakening'
Regan said that without the infrastructure law funding, it would likely take decades longer for districts to make the transition.
"This is an awesome opportunity for us to electrify our transportation system, really ramp up our manufacturing, but also solve very serious environmental and health disparities," he said.
Experts say school buses lend themselves to electrification since drivers have set routes in the mornings and afternoons and go relatively short distances -- and the buses can sit parked in between, charging their batteries.
Maryland has mandated that all new school bus purchases are electric by 2025 while New York will require that all of its new buses are zero-emissions by 2027.
"There seems to be a real awakening that electric is what the future is going to be for the student transportation industry," said Kevin Matthews, the head of electrification at First Student, the largest operator of school buses in North America.
First Student said it expects that about 300 of its 46,000 school buses will be electric as of the first half of this year. It is working with a dozen U.S. school districts to roll out 170 buses as part of the EPA's program.
Every school bus that transports students takes 35 cars off the road, Matthews told ABC News.
"When you convert that to zero emissions, the air quality improvement is even significantly higher," he said. "So the overall benefits are quite high for the environment, for the children and for the communities where the school buses operate."
Kids now 'have to be careful what they say'
Sheila Martinez, who has been driving buses for Montgomery County Public Schools for eight years, told ABC News she loved driving an electric vehicle.
"It's quieter, it's smooth, the [air conditioning] works great, the heat works great," said Martinez, who switched to an electric-powered bus last year. "It's perfect."
Martinez said the electric buses break down less and that she can often just solve any issues herself by resetting the bus' systems, like one would a glitchy computer. She said she has found that the smoother mechanics of her electric bus have also made it easier, physically, on her body as she drives it.
The kids love it, too, she said. But, she added, laughing: "With an electric bus, they always have to be careful what they say because I can hear them."
And that actually makes the experience safer, she said.
"It's better," she said, "because you can pay more attention to what's going on around you."
Montgomery County Public Schools says that the total cost of switching to electric buses is the same as if the buses were diesel-powered, thanks to the thousands of dollars saved each day on fuel costs and on lower maintenance needs for the electric vehicles. (The fleet uses 17,000 gallons of diesel fuel each day, according to the district.)
Its schools are leasing their buses from Massachusetts-based Highland Electric Fleets: The $1.3 million, four-year contract also includes electricity and maintenance, while Highland plans to take advantage of parked buses by pumping their extra electricity back into the grid.
"As a superintendent, I always try to reflect on -- what are the needs of our district and where are places that we are able to save?" McKnight said. "We're building trust with our community by showing them that we're being fiscally responsible."
But not all school districts have had that same level of flexibility to start to transition to cleaner vehicles, even with the federal government's new program, according to Susan Mudd, a policy advocate at the Chicago-based Environmental Law & Policy Center.
Some school districts who do not own their own buses like Montgomery County does -- often lower-income districts that rely on contractors -- have had trouble getting federal dollars due to a government requirement that they identify one diesel bus to scrap for each one that would be replaced with a cleaner one, Mudd told ABC News.
Regan said the EPA's top priority is to take diesel buses "out of circulation" and the agency wants "to ensure that these dirty diesel school buses don't go from one school district to another school district."