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 start working with states to provide “rigorous firearms training” to teachers and other school personnel who volunteer to be armed, said Andrew Bremberg, director of the White House Domestic Policy Council. The White House has not 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.

Bremberg said the administration is backing two pieces of legislation: A bipartisan bill by Sens. John Cornyn, R-Texas, and Chris Murphy, D-Conn., that is designed to improve the accuracy and effectiveness of the National Instant Criminal Background Check System; and the STOP School Violence Act, which would authorize state-based grants to implement violence prevention training for teachers and students.

The administration also is urging all states to pass risk protection orders, as Florida recently did, allowing law enforcement officers to remove firearms from individuals who are considered a threat to themselves or others and to prevent them from purchasing new guns, Bremberg said.

Lastly, the administration wants to better integrate mental health, primary care and family services programs, and the president has ordered a full audit and review of the FBI tip line, he said. The FBI has said it ignored a warning that 19-year-old Nikolas Cruz might attack a school just weeks before he allegedly carried out the rampage in Parkland.

“The president is determined to get to the root of the various societal issues that lead to violence in our country,” Bremberg said. “No stone will be unturned.”

At the Department of Justice, meanwhile, Attorney General Jeff Sessions on Saturday took an incremental step toward banning bump stocks, devices that can make semiautomatic weapons fire like fully automatic firearms.

Sessions submitted to the Office of Management and Budget a proposed regulation on bump stocks. The proposal still requires that office’s approval, and once that is complete, it must be published and public comments considered before it becomes reality.

While some gun control advocates welcomed the move, others argued that it would still be better for Congress to pass legislation banning the devices. Federal officials had in years past concluded they could not legally regulate bump stocks, and the new move to do so is likely to be met with lawsuits from manufacturers of the devices.

For its part, the NRA does not oppose regulating bump stocks under existing law, but does object to new legislation.

In Florida, Gov. Rick Scott, R, defied the NRA last Friday by signing into law a new set of gun regulations that imposes a three-day waiting period for most purchases of long guns, raises the minimum age for buying those weapons to 21 and bans the possession of bump stocks.

“I am going to do what I think are common-sense solutions,” Scott said after the signing. “I think this is the beginning. There is now going to be a real conversation about how we make our schools safe.”

But the new Florida restrictions have drawn opposition from some Republicans nationally. Sen. Ron Johnson, R-Wis., said Sunday on CNN’s “State of the Union” that he does not support raising the age to purchase long guns, such as AR-15 rifles that have been used in many of the recent mass shootings.

“We send our sons and daughters over to Afghanistan, in Iraq,” at age 18, Johnson said. “They defend our freedoms. I think if they do that, they ought to be able to buy a hunting rifle.”

Trump has vacillated in his public pronouncements about guns. He and Republican leaders in Congress have been afraid to cross the National Rifle Association ahead of the November midterm elections because the gun lobby has long been a powerful force mobilizing conservative activists in elections.

At his Feb. 28 meeting with lawmakers, Trump sounded open to new restrictions on gun purchase. “Take the guns first, go through due process second,” he said, winning the approval of Sen. Dianne Feinstein, Calif., and other Democrats who have long sought to toughen gun laws and ban semiautomatic assault rifles.

But NRA leaders then met privately with Trump and the president had an apparent change of heart and backed off more restrictive proposals. Last week, Trump met personally in the Oval Office with Kyle Kashuv, a Stoneman Douglas student who has become one of his school’s few pro-gun rights activists with his frequent appearances on Fox News Channel.

The Washington Post’s Matt Zapotosky contributed to this report.