What role does private security play in crime prevention:
ANSWER 0%
They deter....not prevent
All they do is make the people who are paying them feel better.
My kids elementary (private) school is in permanent lock-down now and you must have a school issued ID to enter. You think a bad guy cares...they'll just bust a locked door...they're only glass.
My wife thinks adding a deputy to every school including elementary will help....what a waste of law enforcement resourses.
I don't have an answer, but I see the government throwing our tax dollars at it to hope it goes away.