COLUMBIA — A state board on Wednesday approved an emergency plan designed to keep school buses running in case unionized drivers in two districts strike.

The State Board of Education voted 10-0 to let a private company bring in certified drivers from other states for up to 90 days. The company, Illinois-based Durham School Services, is contracted to operate buses in Charleston County and Summerville schools.

Unionized drivers in both districts have approved going on strike if they cannot reach a deal on drivers’ pay and benefits by next week.

State Superintendent Mick Zais urged passage of the plan, noting that’s all state officials can do.

It “will provide flexibility to school districts so they can ensure students are transported to and from school if the unionized bus drivers strike,” Zais said.

The Republican schools chief also urged the drivers of Teamsters Local 509 not to strike, saying those affected will be parents who may have no other way to get their children to school.

While South Carolina is the only state to own and maintain a statewide bus fleet, drivers are district employees. The state supplies the buses and fuel for state-approved routes; districts’ responsibilities include employing bus drivers and routing buses.

State law allows districts to outsource their responsibilities. Charleston County and Dorchester 2 are among only three statewide that do. Beaufort County also pays Durham to manage bus routes and employ drivers.

Drivers in those three districts are the only ones who can strike, because they work for a private company. Drivers who work directly for districts are public employees who are barred from collective bargaining or striking.

An idea pushed by Gov. Nikki Haley would result in more districts contracting for bus services, and likely more drivers unionizing.

In her 2013-14 budget proposal, Haley again advocates transferring ownership and upkeep of the fleet to districts.

On the campaign trail, Haley touted privatization of the fleet as a possible way to save money, though experts and former studies on the issue indicate it could cost more. She’s since touted the idea as decentralization, letting districts decide whether to run their own fleets, outsource with companies such as Durham or choose some combinations of the two. She proposes that the state divest itself of all buses by June 30, 2017, and change the funding model.

Haley’s spokesman said the potential strike does not alter her opinion.

“This shows exactly why unions are distracting,” said spokesman Rob Godfrey. “If we privatize our buses, we have choices that allow competition for the school districts and those that work for those companies.”

It would represent the first strike of school bus drivers. A similar threat loomed in Beaufort County in 2007 during contract talks.

Representatives of neither Durham nor the union immediately returned messages Wednesday. The districts are not involved in contract negotiations.

Rep. Jim Merrill, a chief advocate of turning the state fleet over to districts, said the potential strike highlights reasons that opponents give to kill the idea, as well as the need for districts to thoroughly explore companies bidding for contracts, but his support hasn’t changed.

“I’m for decentralization, not privatization,” said Merrill, R-Charleston. “Let people do what’s best for their local school district.”

Last year, legislators gutted his bill to instead create yet another study panel on the issue, which was supposed to issue a report this month.