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Unfortunately, most institutions of higher learning have a blanket "no guns, period" policy. Even if a student is trained and capable, even if he's an off duty police officer, even if he has a security clearance higher than God Himself, he still can't carry on school grounds.
As someone who works on a college campus, all I say say is: Thank G-d. Arming a student population - on the extremely unlikely chance there will someday be a massacre - is going to make campuses more dangerous, not less.
To all the closet Rambos out there, I assure you that over the course of your lifetime, there is a 99.9% chance you will not have an opportunity to pull out your concealed weapon, blow away a Seung-hui Cho, and save a college campus. Get over yourselves.