Brentwood Military Academy was founded by Mary McDonnell in 1902. The school moved sites multiple times under the direction of McDonnell and her family until moving to its final location in 1930. In spring 1972, it was announced that the military academy would not reopen in the fall. The property was sold by John McDonnell to Terry Leavey Lemons and Walter Ziglar, who soon converted the school to
non-profit status. Brentwood School opened in fall 1972 as a college preparatory day school serving Grades 6–10. For the first 5 years, Ziglar served as the President. He was also the chair of the first Board of Executive Directors, which included Bill Badham of
Curtis School and Vern Simpson of
Montclair Prep. The first headmaster was Richman Grant. Grade 11 was added in 1973, and the school graduated its first Senior class in June 1975. Brentwood School remained Grades 7-12 until 1995 when, under the guidance of Headmaster Hunter M. Temple, the school purchased the Marymount Junior School campus and opened the Lower Division. With the opening of the Lower Division in fall 1995, the school became Grades K-6 on the West Campus and Grades 7–12 on the East Campus. In 2001, the Brentwood School Athletics Complex opened on the East Campus. On December 2, 2011, four new modular classrooms were installed at Brentwood School's East Campus. The classrooms were the first zero net energy classrooms in Los Angeles County. In the fall of 2019, Brentwood School opened a brand new Middle School building allowing its 6th Grade to join the Middle School from the Lower School, and increase enrollment size for each grade on both campuses. ==Overview==