What's wrong with a registry, or requiring a license for firearm use? Such measures are put in place for cars, how is a gun registry any different? What is the actual problem if you're going to use it for legal purposes? Passing a range test and basic safety test or whatever it is you have to do to get a concealed carry isn't the same thing as being an effective agent in a school shooting scenario. Legally, the burden placed on an agent of the state is much higher than some joe-schmoe concealed carry citizen. If a teacher accidentally shoots a student for any reason, that school system is going to pay out millions and they just miserably failed one of their students. If that teacher passes a strict vetting process and also wants to opt-in to a lot of extra training (and I do mean a lot, like cops are often under trained in this area as well, evidenced by the situation in Florida) then it could be an option. I just don't see it as a very realistic option at all.