MADISON, Wis. — Wisconsin school bus companies are struggling to find enough drivers before the start of the school year next month, leading some districts to combine routes that make students' commute longer.

Most schools in Wisconsin contract private with bus companies, which spent the summer months trying to recruit drivers. But that has proven to be a challenge this year.

"It's a huge concern," said Dan Kobussen of Kobussen Buses, a Fox Valley-based company that has contracts with 23 districts across the state. "It definitely is the worst I've seen it."

The state's unemployment rate is also at an historic low of nearly 3% this year.

But Steve Roekle, owner of the Manitowoc-based Brandt Buses, said the nature of the job just makes it a hard one to attain. He told Wisconsin Public Radio that bus driving has high barriers to entry. In addition to requiring, a commercial driver's license, drivers must undergo rigorous drug testing and background checks, a physical exam and a motor vehicle driver's history check. Those requirements limit the pool of viable candidates.

He also attributed the shortage in drivers to the state's aging population as baby boomers are now semi-retired.

"We used to get shift workers at factories who after working first shift would come in and drive an afternoon route," Roekle said. "Or before their second shift, they would drive the morning route. But that has dried up as well, because they're working overtime."

Now, districts are resorting to cutting bus service or combining routes due to a lack of drivers. While other districts encourage staffers to drive, said Cherie Hime, executive director of the Wisconsin School Bus Association.

Districts and bus companies "are looking at whether cooks in the school, or janitors or teachers would be a good candidate for bus driver," Hime said.

Kobussen said that in addition to boosting wages, his company pays attention to details of drivers' experience to try to retain workers.

"When it gets this tight, every little bit matters. Is the windshield clean? Is the bus warm? That's the kind of stuff we're looking at. We're trying to make it an enticing job," he said.