The girls eventually discover that they mistakenly enrolled in separate schools, with Agatha, an aspiring witch, going to the School for Good and Sophie, a hopeful princess, attending the School for Evil. The School for Good and Evil book series’ hexology ended in June 2020. However, soon after the final book, Netflix and author Soman Chainani enlisted director Paul Feig for the film adaptation.
Source: https://www.distractify.com/p/the-school-for-good-and-evil-ending-explained