US President Donald Trump has said arming teachers could prevent school shootings like that which left 17 people dead last week in Florida.
A staff member with a gun could end an attack “very quickly”, he said.
Mr Trump floated the proposal as emotional survivors of the 14 February massacre implored him to make sure something similar does not occur again.
The Republican president also backed calls for improved background checks on gun buyers.
Other survivors meanwhile lobbied Florida lawmakers on gun control.
“We’ll be very strong on background checks, very strong emphasis on the mental health of somebody,” Mr Trump told the students from Marjory Stoneman Douglas High School during Wednesday’s televised event at the White House.
“It’s not going to be talk like it’s been in the past,” he added.
The US president also endorsed a proposal long championed by the National Rifle Association (NRA), a powerful gun lobby group.
He pledged to look “very strongly” at calls for educators to be armed with guns.
“If you had a teacher who was adept at firearms,” he said, “they could very well end the attack very quickly.”
“Where a teacher would have a concealed gun on them,” he said, while acknowledging the plan was controversial, “they would go for special training and they would be there, and you would no longer have a gun-free zone.
“A gun-free zone, to a maniac, because they are all cowards, a gun-free zone is, ‘let’s go in and let’s attack.'”
A dozen US states already allow concealed handguns to be carried on college premises, according to the website Armed Campuses. The state of Florida does not.
Mr Trump denied during the 2016 election campaign that he was in favour of guns in classrooms.
The US president listened to pleas for gun reform on Wednesday from about 40 students, teachers and families in the executive mansion’s state dining room.
Some of those at the hour-long event voiced support for Mr Trump’s idea of arming teachers.
But Mark Barden – whose son Daniel was killed in the 2012 shooting at Sandy Hook Elementary School in Connecticut – said more guns was not the answer:
“Schoolteachers have more than enough responsibilities right now, than to have to have the awesome responsibility of lethal force to take a life,” he said.
“Nobody wants to see a shoot-out in a school.”
Andrew Pollack, whose daughter, Meadow, died in last week’s attack – the second-deadliest shooting at a US public school – said: “We, as a country, failed our children.”
“I’m pissed!” he added.
Meanwhile, Florida Senator Marco Rubio also felt the articulate anger of a bereaved parent at a CNN “town hall” event.
Fred Guttenberg, whose daughter was killed at Stoneman Douglas, told the senator that his comments and those of the president’s in the past week had been “pathetically weak”.
“You and I are now eye to eye,” he told Mr Rubio. “Look at me and tell me that guns were the factor in the hunting of our kids in this school this week. And look at me and tell me you accept it and you will work with us to do something about guns.”
Mr Rubio was repeatedly booed throughout his response. He acknowledged that guns were “absolutely” responsible for the death of Mr Guttenberg’s daughter, but reaffirmed his position that “gun laws alone” were not the solution.
He later said banning semi-automatic weapons was “a position well outside the mainstream.”
Hundreds of teenagers from the Washington DC suburbs rallied outside the White House before Mr Trump’s meeting.
Meanwhile, survivors of the shooting poured into the Florida state capital to demand lawmakers restrict sales of assault rifles.
“We want gun reform. We want common sense gun laws,” said Delaney Tarr in Tallahassee.
It was the first organised protest of the youth-led anti-gun movement that has swept the US since the attack in Parkland, Florida.
Other students in Chicago, Illinois; Pittsburgh, Pennsylvania; and Phoenix, Arizona walked out of classes in solidarity.
Some lawmakers in Florida’s state legislature said they would consider raising the minimum age to buy assault rifles – like the one police say was used in last week’s massacre – from 18 to 21.
However, the legislators rejected a proposal on Tuesday to even debate banning such weapons.
Mr Trump’s listening session came a day after he directed his administration to take steps to ban gun “bump stocks”.
The accessories – which enable a rifle to shoot hundreds of rounds a minute – were used by a gunman who killed 58 concert-goers in Las Vegas last October.
That was the deadliest attack by a lone gunman in US history.
The NRA – which contributed an estimated $30m (£21m) to help elect Mr Trump – opposes a total ban on bump stocks but supports some regulation of the devices and some changes to background check legislation.