From 1865 until 1918, Briarcliff Manor served students up to the ninth grade. Before 1918, Briarcliff students who wanted to proceed to high school would attend the nearby Ossining High School. After 1918, Briarcliff introduced an advanced curriculum for high school students. In 1923, four students were the first in a Briarcliff school to receive high school diplomas. In 1928, with the entrance of additional high school students, an extension was added to the Spanish Renaissance-style Grade School for use as Briarcliff High School. The building was located adjacent to the Walter W. Law Memorial Park. The enlarged school accepted students from Croton, Hawthorne, North White Plains, Valhalla, and as far as Granite Springs.