WASHINGTON (Nexstar) — From teachers to bus drivers, many schools around the country just don’t have enough employees. The shortages have forced some schools to temporarily return to virtual learning, something that could happen more often if rising winter COVID cases make shortages worse.

“Some have left because the pay is so inadequate and the work hours are so irregular,” said Sen. Sherrod Brown, an Ohio Democrat.

Secretary of Education Miguel Cardona said the money Congress approved in the coronavirus aid packages should help keep students in the classroom.

“In the short term we need to make sure we have enough staff, maybe bringing back retired teachers and help incentivize that,” Cardona said. “Getting experienced teachers in there is helpful.”

Some districts are considering allowing retired teachers, or those nearing retirement, to work while also receiving their pensions.

Brown said ensuring all students and staff are vaccinated is also critical.

“I think school systems need to be creative,” Brown said. “Some people have left the profoession because they’re concerned about their health.”

GOP Rep. Mike Kelly of Pennsylvania said enforcing mandates could backfire.

“This idea of vaccine mandates has become a political battle,” Kelly said. “I don’t think it’s a policy battle. Once you tell someone you’re going to have to do this they start to back off.”