About twenty years ago I read a book about a school that was off in the woods.
The main character and her friend have to do a meeting with the head mistress. While the friend does well in the meeting, she isn't permitted to attend, mainly due to some test they both did.
As the story progresses, the main character finds that the school is using the students to create master pieces. The spirits of long dead composers and artists possess the students and use them to make the pieces.
The headmistress then ages the papers/paintings in a oven to make them date older. She sells them and gets rich.
I could tell how it ends, but I don't think that would be sportsman like.
So, anyone know the name of this book? I tried asking my school library, but their database lost my history. I didn't fight it since it also lost my owed debts.