Harry Potter is just one of hundreds, if not more, British Young adult and children's books set in a boarding school

So what if Twilight or the CMCs got on the wrong cross-dimensional bus, and ended up in Benkinsop's

https://www.amazon.ca/Blonde-Genius-J-T-Edson-ebook/dp/B01M9D1TMN

In the book, which was originally written as a prospectus for a movie, in the vein of the St. Trinian's school movies, and cartoon strips, an absent-minded professor drops his genius young daughter off at what he thought was an elite girl's boarding school, and vanishes before the administration realized they were the wrong school. He vanished into darkest Africa never to be heard from again.

Then there is St. Trinian's itself. Which could be seen as a British version of the Adam's Family, only set at a girl's boarding school.

Thing is, I, and probably most of the other HP fanfiction writers out there, haven't read those books. If we had, and they grabbed our imagination, then we'd have already started writing for them.