Like all my careers this requires the XML Injector.
I know one guy eagerly awaiting this one. Here's a very meaty package. NPC careers for the Principal, Teachers and the ability to set the Custodian, Caf Worker, and ThrifTea Owner.
This one was weird. The NPC Teacher career exists, but seems to be unused? It didn't seem to be set or referenced in game. Messing with it didn't do any harm either. Well, whatever. I know people want to play as the Teacher so I MADE it necessary to define the High School teacher. Plus it allows you to change the career outfit. The Principal career is a custom NPC one made by me for the same reasons. People want to play as it and that way you can change the work outfit. Immersion, AMIRTE?
This mod will kick out the existing Teachers and Principal!
I didn't think the custodian, Caf Worker, or ThrifTea shop owner were as important (and if I made actual NPC careers for all NPCs nothing would get done) so just set the trait to define those Sims. I dunno, if I get people clamoring for a career for those Sims I may make an NPC one.
In my tests it seems like only the latest NPCs were used, but I don't know. Maybe they rotate and I just never saw it happen.