The chief executive of one of the state's largest school bus transportation providers says driver shortages are causing problems for the back to school season.

NRT bus company chief executive John McCarthy says about ten percent of his workforce isn't returning this school year, just as many students return to the classroom. Many of the largest cities in Massachusetts, including Boston, Lawrence and Cambridge will be affected.

"I've been doing this for 33 years, and I haven't seen anything like this," McCarthy said.

The move has sent many districts scrambling to reroute buses or open early to ease delays, said Tom Hamilton, executive director of the School Transportation Association of Massachusetts.

The reasons for the lack of interest in the jobs is complex. Some bus drivers found alternate employment when many schools closed during the pandemic in March of 2020. Others drivers may fear losing their expanded government unemployment benefits if they go back to work, while others may not be keen to drive a busload of unvaccinated students — even if they wear masks.

"This is a national problem," said Hamilton, who sits on the National School Transportation Association board. "We've done a pretty aggressive social media campaign to get people aware that we've got some issues. We're being up front with school districts."

Hamilton says districts have been given suggestions, including that they should consider earlier bus pickup times, requiring schools to open earlier, putting more kids on a route or multiple sports teams on one bus. Some companies are offering pay and referral bonuses to attract workers. He says the association has also reached out to the Registry of Motor Vehicles and trucking organizations to find interested drivers.

"We’re not sitting here saying, 'Oh, poor us,'" Hamilton said.

Lawrence public schools warned parents on its website to expect transportation delays. A spokesman for the Boston Public Schools says the district does not yet have a clear idea if it has a driver shortage, but has taken precautions just in case. School bus drivers who work for its busing contractor, Transdev, have not yet reported to bid on their bus routes, but will do so on Wednesday.

NRT Bus is one of the state's largest school bus transportation providers. It transports students in most major cities in Massachusetts, including special education students in Boston, and riders in Lawrence, Cambridge, Framingham, Chelsea, Somerville and Lynn. Lynn had to suspend school bus service entirely last April due to driver shortages.

McCarthy said the current number of drivers is about 400 fewer than needed. Another 100 drivers are currently undergoing the required training and certification, which takes 8-10 weeks to complete and won't be done in time for schools' start.

Because would-be drivers are also getting pulled away to work for Amazon, Uber and delivery services that don't require the intensive state certification, he's working with state officials to explore ways to expedite the licensing process.

"We're going to have some bumps as we go through this challenge," McCarthy said, "but we're managing it."

He urged moms and retirees looking for part time work, as well as college students 21-and-older with three years of driving experience to apply for the jobs, which can be part and full time.