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 it never happens 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.