The first San Leandro High School opened at Bancroft and Estudillo Avenues in 1926. In the 1930's, San Leandro changed from an agrarian to a residential community with sub-divisions replacing cherry orchards. San Leandro High was a part of the Oakland School District.
World War II saw rapid transformation of the community. Industrialization and a rapidly growing population created the need for newer and larger schools. On September 12, 1949, students moved into the building which now houses San Leandro High. The old high school building became Bancroft Junior High.
A local election in 1952 unified the two schools under the San Leandro School Board, until then an elementary District. The old building on Bancroft and Estudillo was replaced by the present Bancroft Middle School in 1955 at the same time John Muir Middle School opened on the West side of town. Pacific and Lincoln High schools were added in the 1960's to meet the peak of the post-war baby boom. When enrollments declined, Pacific was closed in 1983 leaving San Leandro High with two feeder Middle Schools and Lincoln Continuation School.
In the fall of 2010, the high school opened the Fred T. Korematsu Campus exclusively for the ninth grade. The mission of the school is to give special support to ninth graders as they transition into high school.
