@Astro I was afraid that would be the case. I suppose I can change my headcanon to reflect the fact that in Simworld, students change dorms, etc. every term instead of every year, the way they do in the universities I'm familiar with. I suppose if I especially like some of the dormies, I can add them to My Households and save them to my Gallery so they're available.
@rongtudjuuu You gave me a lot of help, and I understood your English perfectly! I think I'll have my Sim take two classes sometimes, so he can take some electives. I'll definitely think about creating some residential lots in Britechester so my Sim's classmates won't change so often.
Thanks, to both of you, for your help! I've never "met" a friendlier group of people in a forum like this.