The SROs at my kids school are not rent-a-cops, they are cops. They can't change the laws of physics and get someplace faster, better etc. Police arrived at the Aurora theater in 90 seconds; the cops at my kid's school would have trouble getting from their portables to the back of the first building in 90 seconds. If the building was locked down, it would take even longer.
Columbine High School, Virginia Tech both had cops:
http://www.businessinsider.com/there-were-police-officers-at-columbine-2012-12
I still haven't seen anyone give a real reason that a civilian needs 30 round and larger clips. So they are fun to shoot; go to a shooting range, where the guns are kept, and shoot at the range. Why does a civilian need armor piercing bullets? Why do they need military grade sniper rifles? Why shouldn't these be regulated? The only arguments I've seen against regulations are that it violates the 2nd amendment; which is balderdash. The courts have ruled that regulation doesn't violate the second amendment. No one is saying "take away the guns".