Originally Answered: Searching for a fiction book I once read?
Down a Dark Hall by Lois Duncan
"Kit is accepted into Blackwood boarding school for girls. The place is far out in the country and upon glimpsing the restored ancient building, After her mother gets re-married and plans a honeymoon, Kit is forced to attend Blackwood Boarding School, run by Madame Duret, although Kit feels something dark coming from the school. She was originally planning to attend with her best friend, Tracy, but Tracy didn't get accepted even though she had better grades. When Kit arrives, she immediately confirms something evil about the house. She sees her personal room but is disturbed by the locks only usable from the outside, and meets the teachers: Madame Duret, Professor Farley, and Jules. Jules is the son of Madame Duret, and teaches piano, who seems very interested in Kit. The following day three other girls arrive, Lynda, Ruth, and Sandy.
At Blackwood, each student is taught according to their 'level of learning and ability', independently of the other students. Only three other students show up: Lynda, blonde, beautiful, and rather ditzy, her best friend Ruth, lonesome and rather plain-looking, but smart, and friendly, redheaded Sandy, Madame Duret stating that the school is very exclusive. Each girl held some talent in addition to their imaginations. Lynda Hannah transforms into the next Van Gogh, Ruth can perform and solve complicated math problems, and Sandy writes detailed poetry, this being odd because none of them had been able to do these things before. Kit discovers her inner specialty as well: composing wonderful piano music. Ruth identifies this as "ESP" or extra-sensory perception, and is excited, but Kit is further disturbed, especially after waking up to playing the piano with Jules recording it, confirming her earlier suspicions of hearing music she recognized from somewhere else. After investigating, Kit learns that former students at Blackwood were famous artists who died young and continue their contributions of creativity by using the current students as puppets. Kit asks Natalie, the maid, who had tried to help but was subsequently let go by the seemingly nice instructor, taking a letter from Kit to Tracy. Of the twenty-four former students, three committed suicide, one fell from the third floor of a building (considered an accident), and the other twenty students were put in insane asylums. Kit devised a plan for escape, after seeing some of Lynda's paintings - in particular, one of a woman being horrifyingly tortured - and realizing her health is deteriorating. Kit learns in horror that Madame Duret has been selling the student's works as long-lost artist's inventions..."