WASHINGTON — Education Secretary Betsy DeVos has left it to Congress to decide whether states can use federal funds to purchase firearms for their schools, prompting congressional Democrats to begin a last-ditch effort to restrict those funds.

Conservatives said Ms. DeVos’s stance was consistent with her championing of local school control. But Democrats and advocates denounced her decision as a tacit endorsement of federally funded firearms in schools, and federal policy experts saw the move as an abdication of the department’s core function to help districts navigate the federal bureaucracy.

The Education Department had been considering whether school districts could tap into a $1 billion program intended for academic and enrichment programs after states asked whether school safety measures — including providing firearms and training — would be an allowable expense. But Ms. DeVos essentially punted the question back to Congress, which wrote the law that created the program but was silent on firearms purchases.

Congressional Democrats are planning to push for language in an end-of-year spending bill that would expressly prohibit the use of grant funds for guns.