So do you have a specific example of a school that prompted the question?
Its very possible if it is a Land Grant School it dates to the days of mandatory ROTC. Where all male students attending, even those not seeking a commission, had to participate in at least some perfunctory drill. And the rifles would need to be kept somewhere. While many schools in decades past had far more extensive armaments, especially those that took the military instruction expectations more seriously. It was certainly not unheard of for a school with a sizeable corps of cadets to own a few cannons for artillery drills. Many schools also hosted training units of technical disciplines, or things like flight training or aeronautical engineering during the world wars, and those detachments also would have had to keep their arms somewhere as well.
You may be interested in this thread where I talk more about the history of mandatory ROTC participation at many schools.