11 Books Found

Based on your description:

"A story of a girl that went to this boarding school for rich kids who are smart and the teachers or like the heads want to use her as a demon vessel so they can switch bodies whenever they want. I remember some characters like a guy named Oak, which the girls likes and he likes her. The cover page is like a castel and the colour is blue. She killed her teacher from her old school because of a vengeful demon entred her body, and she accidentaly burned the teacher to a crisp and her best friend got terified her"