I imagine the technology for this already exists.  The impetus for it needs to come from something.  Say the threat of a lawsuit for lack of security on campus.

I'm not sure if a school could pay for it. I guess it depends on the size of the school.

I went to a university where most buildings had this feature. Basic chip inserted into your ID card and all doors have little black boxes wired to a central system where they can deny blocks of people access for certain times and places. I'm sure that if my uni could afford it, it's readily available.

we have this for after hours amittance into dorms at my school..and we're relatively small.. (2750 total students) but it is a great idea, one of the reasons i liked it s much here.

I spent some time living in a dorm at the University of New Orleans that required students to swipe their student ID, then input their own PIN to open the door.  A good system, but when someone failed to give a group of residents security clearance, we were locked out of our own building, and had to constantly ask RAs to let us in for several weeks until the problem was fixed.

I went to Montclair State for two years and they had, what I think, is a great system. Each on-campus ID-card is programmed for only the certain dorm the student lives in. During office hours, there are RA's at the front door personally checking ID's and then scanning them at computers. After hours, to open the doors to your dorm, you had to scan your ID.

You could even have an automated system that allowed entry. Not sure how expensive it would be but if it increases safety to a desirable level with minimal cost then it could work well. You would also be able to stop paying for a security guard.