All 50 states began the current school year short on teachers. And schools nationwide still are scrambling to fill positions in a range of subjects, from chronically hard-to-staff ones such as special education to usually easy-to-staff grades such as kindergarten.

Districts that can't find a qualified teacher may stop offering a certain class or hire a rookie with an emergency credential, a move that could lower the quality of instruction. So lawmakers in several states took action in 2017 to increase the supply of new teachers or raise salaries.

"The teacher labor market is a labor market like any other," said Elizabeth Ross, managing director for state policy at the National Council on Teacher Quality, a nonprofit research group in Washington, D.C.

Arizona, Illinois and Minnesota are among states that have sought to increase the supply of teachers by changing licensure rules to make it easier for people who didn't complete a traditional teacher preparation program.

In Minnesota, for instance, under the new structure aspiring career and technical education teachers no longer need a bachelor's degree to get a teaching license. They can get a one-year teaching license if they have an associate degree, an industry credential or at least five years of work experience. The one-year license can be renewed three times.

Changing licensure rules can be controversial, however. Gov. Mark Dayton, a Democrat, vetoed the Minnesota Legislature's first attempt to change teacher licensing requirements. He argued that lawmakers needed to allocate funding to implement the new rules and questioned whether the proposed changes could hurt students.

The Legislature later folded the licensing changes into an education funding bill, which Dayton signed, although he asked lawmakers to rethink the licensing changes.

Other states have tried to increase the supply of teachers by making education degrees less expensive or shortening the time required to get one. Arizona Republican Gov. Doug Ducey asked the state's public universities to create new scholarships for students pursuing education degrees. Virginia's Democratic Gov. Terry McAuliffe directed the state Board of Education to let colleges and universities offer an undergraduate major in teaching, something the state didn't previously allow.

And some states, such as Idaho, are raising teacher salaries. Ducey called for a teacher pay increase in his state of the state address earlier this year, as did McAuliffe this month.

Oklahoma's Republican Gov. Mary Fallin has championed a teacher pay increase. Oklahoma teachers haven't had a raise since 2008.

But finding money to raise pay has been a hard sell in a state where lawmakers have cut education funding to address a budget shortfall. Funding has dropped so low that some districts are holding classes only four days a week — a schedule Fallin has called "unacceptable."

Oklahomans rejected a 2016 ballot initiative that would have raised the sales tax by 1 percent to support education.

One strategy states can use to attract candidates to hard-to-fill teaching positions is to offer higher pay for those jobs, Ross said. Her organization found that 31 states have created pay incentives, such as offering student loan assistance to new teachers who work in high-need areas. Florida, New Mexico and Utah give extra stipends to all people who teach in shortage areas.