Princess Academy by Shannon Hale
Miri, a young girl who lives on Mount Eskel, has the opportunity to be a princess! The prince must marry and all the girl who live on Mount Eskel must be trained at the princess academy. At first, all the girls are excited, but Tutor Olana is very mean and punishes them unfairly. Miri and all the others stand up to Olana and make sure things are changed.
For a while, things seen to go well, but then the academy is attacked and it is up to Miri to save everyone.
Next book: Palace of Stone