As the father of a 9 year old, and a 19 month old, I would willingly pay for private security, or even better in my opinion, armed and trained teachers. I am leery of having uniformed officers in a school, not because I don't think they would make a difference, but because they would be the first shot in an attack. At the very least, armed teachers in addition to an officer would provide backup for that officer because no one would know who else was armed. The police officer would be a deterrent to some degree, but the possibility of additional teachers being able to assist would add to it.
My thought is if the teachers trained with the assigned officer, that would do so much more to provide an effective defense.