Although I understand the argument, Having worked at a university for about 5 years, there are two issues.
1. 80% of the students are not 21 and in most states can not get a ccw.
2. I fear that most students do not have the maturity to own/carry a firearm, much less engage in lethal force encounters. Many people argue that college is about making mistakes and learning from them. Easy to do when you are hung over and miss a class, not so easy when you pull the trigger.
I think the answer to the "Active Shooter" is a qualified, trained response force on campus, ie Campus Police, Public Safety or security, as well as training the community to recognize and report active violence immediately.