Merston High is a book-only high school within the Monster High book series. It exists only in the book franchise, and is "Monster High" spelled all mixed up. It is Salem, Oregon, and is a very populated school.
It's a large high school with where Sydney Jekyll teaches science and where Principal Weeks is the principal. The ones that go to it are Melody Carver, Frankie Stein, Cleo de Nile, Clawdeen Wolf, Draculaura, Brett Redding, Lagoona Blue, Bekka Madden, Haylee, Heath Burns, Jackson Jekyll, DJ Hyde (or spelled "D.J. Hyde"), Deuce Gorgon, and many, many unnamed others.
Frankie Stein first tried going to a school far away from Salem, but stopped when the normies didn't want her there, and screamed in horror and sheer terror. She certainly goes to Merston High in the Lisi Harrison book series.