WASHINGTON — The White House on Sunday vowed to help provide “rigorous firearms training” to some schoolteachers and formally endorsed a bill to tighten the federal background checks system, but backed off President Donald Trump’s earlier call to raise the minimum age to purchase some guns to 21 years old from 18 years old.

Responding directly to last month’s gun massacre at a Florida high school, the administration rolled out a series of policy proposals that focus largely on mental health and school safety initiatives. The idea of arming some teachers has been controversial and has drawn sharp opposition from the National Education Association, the country’s largest teachers lobby, among other groups.

Many of the student survivors have urged Washington to toughen restrictions on gun purchases, but such measures are fiercely opposed by the National Rifle Association, and the Trump plan does not include any substantial changes to gun laws.

Rather, the president is establishing a Federal Commission on School Safety, to be chaired by Education Secretary Betsy DeVos, that will explore possible solutions, such as the age requirement for purchases, officials said.

DeVos characterized the administration’s efforts as “a pragmatic plan to dramatically increase school safety.”

“We are committed to working quickly because there’s no time to waste,” DeVos said on a Sunday evening conference call with reporters. Invoking past mass school shootings, she continued, “No student, no family, no teacher and no school should have to live the horror of Parkland or Sandy Hook or Columbine again.”

The administration’s proposals come after 17 people were shot and killed last month at Marjory Stoneman Douglas High School in Parkland, Florida, a massacre that spurred officials in Washington to reevaluate gun laws.

Trump has said he was personally moved by the shooting – and by the persistent and impassioned calls for action from some of the teenage survivors as well as parents of the victims – and elevated the issue of school safety in his administration. He has called for raising the minimum age for purchasing an AR-15 or similar-style rifles from 18 to 21 years old.

“Now, this is not a popular thing to say, in terms of the NRA. But I’m saying it anyway,” Trump said in a Feb. 28 meeting with lawmakers. “You can buy a handgun – you can’t buy one; you have to wait until you’re 21. But you can buy the kind of weapon used in the school shooting at 18. I think it’s something you have to think about.”

But the White House plan released Sunday does not address the minimum age for gun purchases. Pressed by reporters about the apparent backtracking, a senior administration said the age issue was “a state-based discussion right now” and would be explored by DeVos’s commission.

At a political rally Saturday night in Pennsylvania, Trump mocked the idea of commissions to solve the nation’s drug epidemic.

“Do you think the drug dealers who kill thousands of people during their lifetime, do you think they care who’s on a blue-ribbon committee?” Trump said. “The only way to solve the drug problem is through toughness.”

Administration officials demurred Sunday night when asked why Trump found commissions an inadequate response to the drug epidemic but an appropriate way to respond to gun massacres.

“There are not going to be one-size-fits-all approaches and solutions, and I think that that is a very cogent argument for having a commission,” said a senior administration official, who would only answer questions from reporters on the condition of anonymity.

The centerpiece of the administration’s plan is Trump’s vow to “harden our schools against attack.” Since almost immediately after the Parkland shooting, the president has advocated arming some teachers as a solution to stopping future massacres.

“A gun-free zone to a maniac – because they’re all cowards – a gun-free zone is, let’s go in and let’s attack, because bullets aren’t coming back at us,” Trump said during a Feb. 22 listening session at the White House with teachers, students and parents.

The administration will begin working with states to provide “rigorous firearms training” to teachers and other school personnel who are willing to volunteer to be armed, said Andrew Bremberg, director of the White House Domestic Policy Council. The White House has not as yet proposed offering states new funding for this training.

Lily Eskelsen García, president of the NEA, the teachers lobby, said last month that “bringing more guns into our schools does nothing to protect our students and educators from gun violence. Our students need more books, art and music programs, nurses and school counselors; they do not need more guns in their classrooms.”

The NRA supports the idea of allowing armed teachers in schools.