Notes on a Scandal (2006)

Barbara Covett (Judi Dench), a veteran teacher at St. George's, senses a kindred spirit in Sheba Hart (Cate Blanchett), the school's new art teacher. The younger woman's charisma intensely draws in the older, and the two become friends. Then Barbara learns of Sheba's affair with a teenage student and becomes the keeper of the explosive secret.