As a new school year nears for more than 50 million U.S. students, many districts worry how they will get children to school.

The country has a shortage of school-bus drivers which 22 percent of private bus contractors call "severe," according to a recent survey by School Bus Fleet Magazine.

Five percent of school-bus contractors are "desperate" to find drivers, the survey found.

"We're seeing some school districts having to cut school-bus routes or consolidate them, having fewer stops," said Thomas McMahon, the magazine's executive editor said.

Elementary-school bus driver crochets toys for every kid on her route

City bus driver takes in young child wandering streets in the middle of the night

The director of transportation for the Douglas County school district in Colorado said bus driving is not as attractive a job as it may have been recently.

"The economy's better so people are going back to jobs that they had done previously, or they find the need to stay at home," Donna Grattino told ABC News Denver affiliate KMGH.

The Denver-area district still needs at least 40 more school bus drivers and is considering enlisting stay-at-home parents to help fill the gap by allowing them to bring preschool-age children with them on the route, Grattino said.

"As long as they can walk up on a bus, we can get them into a car seat and make sure they're safe," she said.

But becoming a bus driver can take time.

The process to get a commercial drivers license, including obtaining a permit, training time and taking the test can in many states take up to 12 weeks, according to the New York State Department of Motor Vehicles. Drivers also often have to undergo extensive drug tests and background checks.

Average starting-pay at the 50 largest school-bus companies rose to $16.90 an hour in 2017, up from $16.24 in 2016, School Bus Fleet said.