MINNEAPOLIS — A shortage of substitute teachers is putting Minnesota schools in a bind.

As school districts struggle to pull in substitutes, teachers are heading to class sick. Principals are splitting up children between classrooms or even taking up teaching duties. It’s a problem nationwide, driven by more substitutes finding permanent work while other teachers leave the field entirely, drying up the pool of retired teachers that pinch hit when needed.

In Minneapolis, the substitute teacher pool is 516 this school year — down more than 60 from last year.

“It’s a crisis,” said Duluth teacher Bernadette Burnham. “It’s another layer of stress for everybody.”

The shortage has had compound effects. It’s prevented some teachers from attending professional development days, while also putting extra pressure on teachers to show up every day.

“Some are being asked, ‘Well, how sick are you? Do you think you can make it through the day?’?” Burnham said.

Some school districts have tried boosting pay for substitutes, who teachers say are generally paid much lower wages, but others doubt whether that will make a dent in the shortage.

Minneapolis Public schools are working with the teachers’ union to increase pay for substitutes, human resources director Maggie Sullivan said. The district is also experimenting with a plan to dedicate substitutes to specific schools in hopes that will give substitutes and principals more stability.

Thomas McCarthy, teachers’ union president in South Washington County, said the issue is with the makeup of the substitute teacher pool. It’s traditionally been made up of new teachers trying to break into the field and retirees. But lately, he said, the young teachers aren’t there.

“That would indicate something about what’s happening in our field in the state,” he said.