Mike McDaniel nails it in his post:
“A model policy for arming school staff should look like this:
(1) Rationale: Staff are armed because an armed attack is possible at any school and at any place in and around any school at any time.
(2) The police cannot deter attacks, nor can they arrive in time to save lives. Any school relying on the police is knowingly accepting some number of wounded and dead based entirely on traffic patterns, the number of officers available when the call goes out, the lack of marksmanship of killers, in effect, dumb luck.
(3) Fundamental Principle: to have as many armed staff members present in every school as possible, so that when and wherever an attack takes place, there will be multiple armed and capable adults ready, then and there, at that instant, to save lives…”
Source: Stately McDaniel Manor – Mike McDaniel <— Read more here