It doesn't matter. Just because you want to keep making these little deviations so that you can try to explain why you can use government force against people doesn't mean that you're talking about something relevant. Young adult, old adult, middle aged adult; it doesn't matter. They are ADULTS. That's what matters. At 18, regardless of what you believe about brain chemistry, all the rights and privileges and responsibilities of a person are recognized. Asking for "trouble" or not, it's all aside. Your personal feelings about maturity are not to actually influence the rights and liberties of others.
Everything you have said is essentially this "I don't think there should be guns on campus, therefore all adults should have their rights infringed upon and prevented from having guns because I think it would be better this way."
If you think that makes a coherent and valid argument, you're fooling yourself. You cannot infringe upon the rights of others just because you feel like it. Not justly. Your feelings are not proper argument against the rights of others. That's the bottom line. You can feel any way you want, but just because you feel something doesn't give you the just power to use government force against the rights and liberties of the individual. You have to have PROOF. For the love of all that is holy, can you not understand that point? You have no proof, only assumption, supposition, and feelings. You have a few administrators who don't want it, but it's all based on the same flawed logic. Without data you cannot do what you want to do because what you want is an act of government force and coercion against the individual. For that to be done, you need evidence, you need proof, you need something more than some dumbass assumption that "there is no place or need for guns in the classroom" (which is again YOUR ASSUMPTION and not proper argument).
The rights and liberties of all adults are fully recognized. That's it. I have SHOWN you that in places where this is legal, there has been no problem with it. You have shown nothing but assumption, supposition, and feeling. No proof, no numbers, no logical and rational argument. You feel they are immature, you feel that it would be dangerous (even though no probabilities are actually affected). That's all you have, and none of it makes for proper argument for government force against the rights and liberties of the individual.
And that's the bottom line.