The proposal of arming the teachers fundamentally misreads the source of 10 fold factor of this type of event (non terrorist mass shootings) in the United States.
This type crime presents itself as an an opportunity potential shooters, always with a profile of an intense sense of physical inferiority, sexual inadequacy, social isolation, personal persecution.. as means of compensation and revenge.. BECAUSE of the prominence of guns and gun culture in USA.
The NRA promotes a culture that portrays gun ownership as a badge of manhood; the home as a fortress against dark forces that lurk in society; government, community and police as an inadequate response to this pervasive threat.
The ONLY way to reduce this is to control guns. Like they do in Canada, Europe, Japan.. which allows responsible ownership of hunting weaponry but severely limits that for 'protection'. And certainly does not allow the wearing of concealed handguns as a 'right'.
In Florida it is estimated that 10% of adult population is armed.. and it likely hasn't saved and single life and produces any number of horror stories of mistaken motives or road rage or domestic altercations ratcheted up to fatal consequences by the presence of a gun. It'll be the same with teachers, and will cultivate more shootings than it will prevent.
The Second Amendment was NOT a free for all for gun nuts, murderers and psychopaths. It was intended to protect the right of communities to establish Citizen Militias.. by their nature highly regulated and disciplined structures.. as a bulwark against tyranny.
It has morphed into this unrecognizable and irrational construct of gun ownership as a facet of individual liberty by the lobbying of the NRA. This is a group with 5 million members and the organization, financing and cunning to make this small minority and decisive force in American legislatures.