It is very, very wrong for a civilised country to ask teachers to kill students. There is a world of difference between firing a gun to shoot a target or hunt an animal and using a gun to kill a child.
In hind sight it's easy to imagine the circumstances when a teacher could stop a mass shooting, but the reality is that the police make mistakes and they deal with guns and criminals every day. What happens when a teacher makes a mistake? What happens when a teacher thinks a child is reaching for a gun, but it turns out to be something else? What if somebody else gets injured or killed?
Is it the teachers fault if they can't stop the shooter?
What if great maths teachers just don't want to shoot people?
Are teachers and police and soldiers supposed to share the same qualities?
Are teachers going to be chosen according to their ability to stop a suicidal teenager grabbing their gun?
Trump is now saying:
"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. 20% of teachers, a lot, would now be able to immediately fire back if a savage sicko came to a school with bad intentions".
He thinks 20% of teachers have military experience, can instantly identify 'savage sickos' and they could "immediately fire back"? He watches too many action films . Roughly 1 in 3 Americans own guns, and it's very unlikely that 2/3 of them would happily kill a person (despite what some of them might imagine).
Teachers might be able to help Trump with his English, but they aren't a cheap way to solve the gun problem.