I hear you and understand but at the same time do you realize you are taking about turning schools into prisons? I just don’t think that is the answer. I would rather see a bunch of retired grandpas with military or LEO backgrounds volunteering to roam the halls (with CCW).
Even better, end the indoctrination centers. If people want or see the need to receive education past the 6th grade let them pay for it themselves and chose for themselves the facilities that will meet their needs with the assistance of their parents. No more free public indoctrination centers, no more “school shootings”. Sell the properties and buses to reduce public debt.
Prison??? I didn’t mention walls or fences or guard towers and you jump to the conclusion of prisons??? My point was to make schools the opposite of their current status of soft targets without becoming visually objectionable. Your grandpa idea has value IMO as another element of defense in depth, along with armed teachers who have the late coach’s attitude. My suggestions are just the outer perimeter things that reduce the threat possibly reaching the inner response team.