Trump voiced support for the idea during an emotional White House meeting with students who survived the shooting and a parent whose child did not.
“If you had a teacher ... who was adept at firearms, it could very well end the attack very quickly,” said Trump, who acknowledged the idea would be controversial.
He sat in the middle of a semi-circle in the State Dining Room of the White House, listening intently as students wept and pleaded for change. He vowed to take steps to improve background checks for gun buyers.
The meeting included six students from Marjory Stoneman Douglas High School in Parkland, Florida, where 17 students and educators were slain on Feb. 14 by a gunman with an AR-15 semi-automatic assault rifle in the second-deadliest shooting at a U.S. public school.
“I don’t understand why I can still go in a store and buy a weapon of war, an AR,” said Sam Zeif, 18, sobbing after he described texting his family members during the Florida shooting.
“Let’s never let this happen again please, please,” Zeif said.
Andrew Pollack, whose daughter Meadow Pollack, 18, was killed, shouted: “It should have been one school shooting and we should have fixed it. And I‘m pissed - because my daughter - I‘m not going to see again.”
Trump said his administration would emphasise background checks and mental health in an effort to make schools safer.
“We’re going to be very strong on background checks, we’re doing very strong background checks, very strong emphasis on the mental health,” Trump said.
“It’s not going to be talk like it has been in the past,” Trump said.
Trump’s support for any tightening of gun laws would mark a change for the Republican, who was endorsed by the National Rifle Association gun rights group during the 2016 presidential campaign.