Yeah, that detail situation sounds like a disaster waiting for an opportunity to happen. The last school I worked at did not allow firearms even when carried by licensed personnel like us security people–only sworn peace officers allowed to carry on campus. We did go in civvies for the very reason you stated (and likely to save the state money on uniforms, if the truth be told!) However, it did serve to make us a little more approachable by the students, I think.
Wanted to comment a little on your goal to have a mounted SAR team, and be able to fight from a mounted position. I’ve worked with horses most of my life, and a well-trained horse can be taught not to panic even when a gun is fired from the saddle–but that type of scenario is rather rare these days. Some ranches out in the back of Tenbucktoo might have working horse trained for this, and exposition mounted cavalry teams as well, but finding a good team that can train their horses, AND have good enough horsemanship to pull it off, might be a bit tough. I know you’ve mentioned working mounted SAR before, so I’m probably preaching to the choir, LOL, so please forgive me if that is so. Just thought I’d mention the extreme flight-or-fight response in prey/herd animals like horses, is painstaking work but doable with a good trainer. I do think the mounted SAR team is a great idea!