Montgomery County officials are exploring the feasibility of using public school buses to serve private and parochial institutions to reduce traffic congestion in the morning and afternoon rush hours.

County officials disclosed Wednesday that they have asked both religious and non-sectarian schools to participate in a pilot program to test the idea. Four religious schools have agreed so far: St. Jude Regional Catholic School and Melvin J. Berman Hebrew Academy in Rockville, and St. Francis International School and the Torah School of Greater Washington in Silver Spring.

The county’s transportation department will bill the schools for 22 percent of the cost for buses and driver time — the same proportion that Montgomery Ride On passengers pay in fares for operation of the bus system, officials said. The pilot program is expected to cost between $400,000 and $600,000 in county funds, and a full program would probably cost far more.

County Executive Isiah Leggett (D) said he authorized the venture after hearing from educators and parents about traffic tie-ups on the daily drives to and from school. Getting some of the county’s 30,000 non-public school students out of cars and onto buses could relieve some of that congestion.

“We have all these kids on the road,” Leggett said. “It’s something that begs for attention.”

Other school systems, including Charles County, have been serving non-public students for many years. Leggett said that in his native Louisiana, such systems have worked well.

County officials have had a working group studying the idea since January, but they had not disclosed that a pilot program was underway. Leggett said an extensive public airing at this point is premature.

“We’re a long ways from any kind of full implementation,” he said. “We’ll have a more robust discussion sometime in the future if we find this has the kind of potential for a more thorough utilization in the county.”

Officials said that the initiative will not divert any resources from Montgomery’s school system, which uses 1,137 buses to serve about 100,000 students each school day.

The idea is to use buses that are idle during gaps in the school system’s daily bell schedule. In the mornings, that would be a window of about 30 minutes between the first middle school bell at 7:55 and the 8:50 start time for many elementary schools.

Last week, for example, buses began morning service for some of Berman Academy’s 700 students. They assemble at two locations — Churchill High School in Potomac and the school system administrative center on Kemp Mill Road — for the trip to Berman, which is off of Aspen Hill Road in Rockville.

Whether the plan is sustainable at a larger scale is unclear. The county’s school system is under pressure from parents to establish later start times, especially for high schoolers, and is reviewing its bell schedule. Any changes could scramble the pilot program.

“The operating window that is fairly limited in the current bus schedule could be non-existent in some other bell schedule,” said Todd Watkins, the school system’s transportation director.

Afternoons will be less of a challenge, officials said. Most county school buses are done with their regular runs by 4:30, a time when many non-public schools with extended days could use them.

Tobias Harkleroad, principal at St. Francis, said the buses will be a huge improvement because of the school’s location, off chronically clogged New Hampshire Avenue just south of the Beltway in eastern Montgomery.

“Anyone who knows this part of the county knows it’s a nightmare in terms of traffic,” Harkleroad said. “We have a number of families that live all over the place. We want to try to make the commute easier for them.”

Leggett said lawyers have advised him that there are no issues involving separation of church and state because the bus service is also being offered to non-sectarian private schools. So far, however, none have opted in.

Elizabeth Shannon, communications director for the McLean School in Potomac, said Wednesday that officials there are interested and in discussions with the county.

John Matthews, a former Montgomery schools transportation director who is working as a consultant to the county on the project, said he was aware of “some apprehension” from parents about putting children on buses with public school students. Some parents of children who wear uniforms are concerned that they could be bullied, he said.

The County Council plans to discuss the idea in the next few weeks, and Leggett is expected to ask for a supplemental appropriation to fund the pilot program.

Council President Craig Rice (D-Upcounty), chairman of the education committee, said he is open to the idea but is concerned about the long-term costs.

“If we can come up with a way that is cost-efficient, then I’m supportive of that,” Rice said. “But the jury is still out on that.”