Top GOP lawmakers on K-12 issues in the U.S. House of Representatives—including U.S. Rep. John Kline, the chairman of the education committee—are worried that the Obama administration has been throwing “roadblocks” when it comes to student participation in the D.C. Opportunity Scholarship program, which helps low-income students in the nation’s capital cover the cost of private school.

The program serves less than a couple thousand students and costs the feds just $20 million a year—moisture in the U.S. government budget bucket. But it has long been a political flashpoint in Congress, partly because it’s the most prominent federally-funded voucher program. Some congressional Democrats have been trying to eliminate the program, saying it’s not the federal government’s place to pay for vouchers. But the program is a big priority for Rep. John Boehner, the Speaker of the House.

Last spring, the administration and congressional Republicans agreed to a deal that essentially boosted the number of slots in the program from 1,615 to about 1,700, in part so that there would be enough kids to perform a rigorous evaluation of the program. Everything you ever wanted to know here.

But Kline and two of his GOP colleagues—including Rep. Darrell E. Issa of California, the chairman of the House Oversight and Government Reform Committee and Rep. Todd Rokita, R-Ind., who oversees the House subcommittee that deals with K-12 education, are now worried that the administration has been putting in place obstacles to students’ participation in the program.

“Our offices continue to be concerned that the department is pursuing arbitrary policies and procedures that will hinder implementation of the program,” the lawmakers wrote in a letter sent Feb. 1 to U.S. Secretary of Education Arne Duncan. Check out the letter here.

They want to know what actions the department has taken to make sure as many students as possible are included in the program, and want an accounting of its funding, by Feb. 22.