My university's college radio station runs the full gamut of what you described. It's kind of interesting how they do it.

Broadcasting students get to have a show after completing certain core courses. They begin over summer, when listenership is very low. Listening to the station in late June/early July is adorable. I should actually tune in today, now that I'm thinking about it, because it's around time for all the baby broadcasters to be doing their beginner shows.

Students must have the option to end their show at some point, because a lot of student broadcasters just kinda disappear. Others, though, will stay on for 2 or 3 years as they finish their degree. Some of them become VERY good.