Berkeley Hall School was founded by Leila and Mabel Cooper, sisters from Iowa. Prior to founding the school, Leila taught at the Westlake School for Girls in Los Angeles and Mabel studied music in Paris, Boston, and New York. During the summers, the sisters worked together, running a successful summer camp for boys in the San Gabriel Mountains.
When a family of the Westlake school moved to the then-outskirts of Los Angeles, they thought so much of Leila that they promised their support if she would open a school. She accepted and Berkeley Hall opened its doors in 1911. Named after its original location in Berkeley Square, BHS' first campus was located in West Adams Heights, one of the grandest areas at the turn-of-the-century, featuring tree-lined streets and easy access to downtown Los Angeles via electric streetcars.
Berkeley Hall opened with 46 students enrolled, including several boarding students. From the beginning, importance was placed on moral education as well as academic. Leila stated, “I feel much of the success of the school work is due to [...] the cooperation of those who saw that school work is a medium for character training and not merely an end."