Most likely, even less-lethal weapons, especially the projectile types, will be banned on campus. Situational awareness is always good. Make sure you carry a cellphone and subscribe to any campus alert type services offered. Know the on-campus emergency phone numbers, 911 will get you to them, but only indirectly and a bit slower. Know your campus's emergency plans, procedures, alarm signals, call box locations, etc.

Campus crime tends to be grossly under-reported, but are generally pretty safe, depending on the general neighborhood, degree of access, etc. I always encouraged my night students to try to park in the same area and leave as a group, and offered to escort any student to their car after class. Know your classmates. Know who is a familiar on-campus face and who may not belong there. Be sensitive to fellow students under too much stress, isolation, etc.

If your classroom doors open in towards the classroom, a simple wedge to block the door from opening, kept in your backpack, might be real handy. Different doors require different solutions. A bicycle lock might hold double doors closed, for example.