I'm a big fan of Topeak's rack and bag combinations.

But if you're leaving the bike and walking around campus, it's also worth considering how easy your gear will be to carry when you're not on the bike.

When I'm just going to work, my Topeak bag is great. When I'm biking somewhere and then doing some wandering on foot, I would rather have a backpack or satchel. I still don't like wearing a backpack or satchel when riding, but I will put it into a rear basket or a grocery bag pannier. The basket or pannier will stay on the bike, and backpack will go with me.

I find that a balanced load isn't a huge issue on the back of the bike unless you're carrying quite a bit. One rear pannier with a backpack in it doesn't affect my balance. But a rack-mounted basket will center your load, if that's an issue. In addition to my Topeak rack and bag, I have Topeak basket that replaces the bag when I want to bring a backpack.