Professional School Counselor, Wayne Davis, center, greets students as they get off the bus on the first day of school at Greenbelt Middle School in Prince George’s County in August. Prince George’s parents continue to worry about a problem with late school buses. (Sarah L. Voisin/WASHINGTON POST)

It’s not unusual for Claire Mudd, a freshman at Eleanor Roosevelt High School in Greenbelt, to arrive 20 minutes late to her foundations of technology class. At least once, Mudd showed up even later, halfway into second period.

The tardiness isn’t Claire’s fault. Her Prince George’s County school bus is chronically late, arriving long after the first bell rings, and part of a district-wide problem that dates to last year.

Schools buses in the county that continue to arrive late have not only caused an inconvenience for students, but parents worry that the ongoing problem could have a negative impact on grades.

“It really puts the kids at a disadvantage, and it’s not fair,” said Sheila Mudd of West Laurel, whose daughter Claire attends the county’s top-performing school. “She is missing the first 20 minutes of a 45-minute class.”

Mudd said her daughter is fortunate that she does not have a more challenging class during first period, as she isn’t nearly getting full instruction. One student in Mudd’s neighborhood who rides the bus with Claire regularly misses her Advanced Placement English class, she said.

County officials said they are working to fix the problem, which stems from a shortage of drivers at the beginning of the school year.

Thomas Bishop, director of transportation, said the school system has hired nearly 150 new drivers since August, but some of the new hires have decided to work part time, requiring the use of substitute drivers. Some of those drivers appear to be unfamiliar with their routes and have been getting lost, parents said.

Bishop said he has 30 full-time drivers in training, and once they are on their routes, the department should be at full capacity. Bishop said he also will continue searching for more drivers.

The bus driver shortage came as the department rolled out a new cost-cutting transportation policy in August that reduced the system’s fleet by 130 buses, combined middle and high school students on some of the routes, consolidated drivers’ bus routes, and cut the number of stops by 2,350. The policy, which was projected to save the school system $10 million, also raised the maximum distance elementary school students can walk to school from 1 to 1 1 /2 miles.

Despite the driver shortage, Bishop said the county has made improvements since last year. For example, 30 percent of the 60 buses at Henry A. Wise Jr. High School in Upper Marlboro were arriving late, according to a November 2011 survey by the Council of Great City Schools, an organization of the country’s largest urban school systems. Today, because of the new drivers, there are only a few late bus arrivals at Wise, school officials said.

Those sporadic late arrivals are due to traffic and weather conditions, or a substitute driver’s unfamiliarity with a route, said Lynn McCawley, a school system spokeswoman.

McCawley said the school system does not have the software to track bus arrivals and streamline routes. Schools self-report, and the data is not “collected in a reportable format,” she said. The school system plans to buy tracking software this year.

Nancy Garner of University Park said her son was routinely arriving 20 minutes late to his calculus class because his bus driver was getting lost on the way to Eleanor Roosevelt.

“It was frustrating,” Garner said. Her husband began driving him, and now her son has his own car. But Garner said she is not certain what impact the late arrivals and missed instruction had on her son. “It’s tough,” she said. “I don’t know whether he’ll rebound from that.”

County Council member Mary Lehman (D-Laurel), who earlier this month waited more than 30 minutes for her daughter’s bus to arrive at her stop, said she has received numerous complaints from parents who have had to deal with buses that either arrived late or never appeared at all.

Lehman has directed her staff to contact the 20 schools in her district to find out the extent of the problem. She said she has expressed her concerns to top schools officials.

“I can’t even underscore enough how disruptive this is to these kids,” Lehman said. “It has a domino effect. Everything is thrown off.”

Briant Coleman, a spokesman for the school system, said Lehman “has a legitimate concern,” one that school officials “have worked to fix” on her route.

Coleman said a GPS system has been installed on several buses. Additional drivers have been placed on the route, which allowed officials to reduce the number of stops, he said.