School schootings per capita (2009-2018):

USA: 933 * 10^-10

Rest of World: 7 * 10^-10

Having a pretty good statistical significance comparing both buckets, school security and police armament for sure does not seem to have a positive relation with a reduction of shootings.

Nobody wants to hear the solution, but it's pretty clear: If you want to reduce the number of gun fatalities in schools, you need to stop sending people there.

(/s)