>>149362319
Counterpoint: Janna remained a consistent member of the cast for the simple fact that she was interesting. They gave her an interesting enough personality that they kept her around even after they dropped Earth as the main setting. Why? Because she had a personality that could interact with the weirdness of the show and produce something of value from it.
If Janna had just been a one note side character with a personality reliant on the school setting to work, she would have been left behind like everyone else. The weirdness of the show needs interesting characters to bounce off of, most of the school just wasn't up to snuff.
Though, after some consideration, I do think the classmates as presented could have worked, but that would depend on Star actually being a freak. Star isn't really a wacky gremlin like a lot of people headcanon her as, outside of a few episodes. She's a magical princess with a superweapon, but for the most part, she's just, like, a normal teenage girl.
This isn't "let's put a cryptid in the U.S. public education system and see what happens", This isn't Mothman's first semester in high school, It's a normal person who's detached from the normal social hierarchy because she has a magical wand that can create anything she wants on the fly and shoot death lasers.