The problem with this solution to school shootings is that both modern "teachers" and spree shooters are universally Leftist and functionally borderline mentally retarded.
Ponder this: Over the last forty years, since the Bolsheviks have pushed the concept that every pupil "needs" college, it has been the habit of academia to shovel the bottom of the barrel students into eduction and journalism.
These are now the sources of the daily news items of Zero Tolerance stupidity, and you want to promote morons with guns?
Some of the teachers here in Newtown are Veterans, and some are regular shooters with pistol permits. Not all teachers should be armed for the sake of doing so - not all citizens aren’t capable of that responsibility. But those who are able and willing to be trained? Why not!