Public incidents of multiple shooting are little more frequent in the US today than in 1990.

In other words, people's perception that the danger has greatly increased is misinformation.

Furthermore, 30 or so deaths per year in a country as big as the US do not amount to a danger worth worrying about. By contrast, car accidents kill around 40,000 people per year in the US. This is also a tiny fraction of the total number of people killed with guns.

I conclude it is harmful to traumatize millions of schoolchildren with drills about what to do in that exceedingly unlikely situation.

It is an exaggeration to refer to these incidents as "mass shooting": we should limit the term "mass murder" and its variants to cases where hundreds or thousands of people are killed.