I believe the old saying is, "fight fire with fire". A much more effective strategy than advertising schools' defenselessness with "This is a gun-free zone" signs, on the whole:
Roughly forty school districts in Ohio allow teachers to pack concealed guns in the classroom, and more and more of them are getting trained on how to stop an "active shooter."
"[The s]afety of our kids should not be a controversial issue. This is not about guns," Jim Irvine, of FASTERsaveslives.org and the Buckeye Firearms Foundation, told Fox News.
"For nearly sixty years, not one student has died from a fire. That is due to a redundant, overlapping approach to safety. We should be copying that same method for incidents of violence in our schools. You need something that is effective. Show us another method and we would invest in it." [emphases added]
Of course, leftwingnut gun restrictions aren't meant to be effective, because they are ideologically driven. Real-world, on-the-ground results are irrelevant to them; reality must be conformed to their Narrative, not the reverse, no matter how many, in this case, teachers, administrators, and school children have to perish.
Additionally, like with every other incarnation and manifestation of gun control, the implication of "gun-free zones" is that teachers, administrators, and school children are the suspects and potential criminals and perpetrators of "gun violence," and must therefore be disarmed and kept that way. No thought at all is given to anybody outside the schools who may not be too particularly heedful of gun laws and might have a macabre fondness for human target practice and is/are sufficiently literate to be able to read "This is a gun-free zone" advertisements.
There's another old saying that goes, "mutually assured destruction". In the Cold War (i.e. World War III) it was the basis for the very successful deterrence policy that was the reason that Cold War never turned nuclear-hot. The same principle applies in the microcosm as it does in the macrocosm. If a would-be "active shooter" knows that a particular school, like the ones in these forty Ohio school districts, are NOT "gun-free zones" and that teachers and administrators conceal & carry, and the wannabe gunman doesn't and can't know which ones are and which ones, if any, aren't, they will be less likely to go on a bloody killing spree in that particular school. They'll look for targets that they know are "soft," like ones that advertise themselves as "gun-free zones".
It is, indeed, not about guns. It is about common sense. And if the latter were as plentiful as the former, there wouldn't be any "gun violence" problem. Hopefully, more school districts around the country will follow Ohio's example.