Classen High School, constructed immediately following the close of World War I, is the oldest high school building in Oklahoma City. Classen opened as a junior high school in 1919. The land was part of an area being developed by the early Oklahoma City real estate developer, Anton H. Classen. A total of 6.33 acres was purchased by the Oklahoma City Public Schools Board of Education for $55,100. The building was constructed at a cost of $420,500 by the Holmboe Construction Company. The two story brick building was enlarged in 1921, 1923, 1925, 1934 and 1957. The school was converted to a high school in 1925.
Classen School of Advanced Studies (CSAS) is the premier school of its kind in the state of Oklahoma. CSAS offers eligible qualified students of Oklahoma City Public Schools in grades six through twelve a rare and dynamic educational opportunity. Two complementary and challenging college preparatory plans of study are offered: the world recognized International Baccalaureate Diploma Program and the nationally recognized Visual and Performing Arts Program. The school opened in August of 1994 with an enrollment of 647 students in grades six through ten. Classen School of Advanced Studies graduated its first senior class in May of 1997. Classen SAS is accredited by the North Central Association of Schools and adheres to a college preparatory curriculum.