School shootings are not the problem. School shootings are a symptom of problems in the enveloping social and economic systems.
Because the problem is not in the schools, and the schools are not causing school shootings, changing the schools will not prevent school shootings. More police presence, mental health professionals in the schools, arming teachers, metal detectors will not solve the problems in the enveloping systems, so the symptom, school shootings, will remain.
As it is the MO of politics, to change as little as necessary in order to get legislation passed, government will continue to try to change the schools as it is more popular than changing the social and economic systems of which schools are only a part.
As politics is a conflict resolution process, it will view school shootings as a conflict between shooter and authorities. (when your only tool is a hammer, everything looks like a nail) and the possible solutions will be limited to "take away the guns" or "increase the number of LE guns in the schools". Neither will solve the problem, because the problem is not in nor caused by the schools.
Good problem solving does not begin by assuming you know what the problem is.