"Highly trained, gun-adept, teachers/coaches would solve the problem instantly", he said, arguing that the policy would be a "great deterrent".
"This would be a major deterrent because these people are inherently cowards", he said of shooters.
The students and their parents appealed to him to press for stricter gun controls.
At one point while talking about arming teachers, Trump asked: "Does everybody like that idea?"
"What I said was to look at the possibility of giving 'concealed guns to gun adept teachers with military or special training experience - only the best", Trump said in a Twitter message. He did not indicate how he arrived at this number.
"Not for teachers! If you have a gun at home and it's licensed for you to have personally - to be in your vehicle or at home, don't bring that around children and say that that's OK", she said.
First National Bank won't renew contract with NRA
It's been almost 10 days since the deadly shooting that left 17 people dead at Stoneman Douglas High School in Parkland, Florida . Hertz has joined several other top auto rental companies in cutting ties with the National Rifle Association ( NRA ).
Kingsburg Joint Union High School allowed teachers to carry concealed guns last school year until Governor Brown signed a bill in October to make schools gun free. Some have pointed out that an armed sheriff's deputy was on patrol at Stoneman Douglas the day of the shooting, and failed to confront the gunman.
The only small glimmer of hope from this bad episode is that young people across America have started to mobilise and have become motivated to seek real gun control law changes. "You need 100, 150 security guards", Trump said.
What does the proposed idea mean for local law enforcement?
Addressing a gathering of young conservatives, he bolstered Mr Trump's call to arm teachers and offered free training.
Instead, Stevenson said, Boulder Valley wants to create "hard targets" by making it difficult for someone intent on doing harm to get access to students or faculty.
Trump also praised Wayne LaPierre and Chris Cox, two officials at the National Rifle Association, the country's top gun lobby, that is opposing nearly every restriction that gun opponents have advanced in the aftermath of last week's rampage.
Nikolas Cruz, a former student at the school, allegedly used an AR-15 semi-automatic assault rifle to kill 17 students and educators. "I can not imagine having that responsibility of carrying a gun".