Satan's School for Girls (1973)

Satan's School for Girls is set within the grim walls of Fallbridge College for Girls. Hoping to learn the truth behind the "suicide" of her younger sister, Beth Hammersmith enrolls in Fallbridge under the assumed name of Karen Oxford. Our heroine soon learns that the school is in the clutches of a coven of witches called "The Five" -- and that she herself has the right satanic qualities to enable The Five to take over the world