Allow trained teachers to have Weapons' Safes/Carry weapons on them to deter mass murderers

A mass murder wants to kill as many people as possible. They would be deterred if they knew they might encounter a marshall/specially trained teacher who could stop their plans. It works on airplanes. Our banks, airports, malls, celebrities, politicians, etc are protected by armed men. Why not protect our children? In regard to safety issues, police officers are statistically shown to be in as many weapons violations as carry-permit owners. A gun in a classroom is seconds away while a call to police could mean our childrens' lives. At the very least why can we not implement weapons' safes in certain offices/classrooms, or palm print only firearms? This would be more feasible than turning all schools into Fort Knox/ hiring police/special security for each school. Preparation is key.