GLEN OAK SCHOOL was founded in 1969 as an all-girls' school by the Religious of the Sacred Heart (Madams of the Sacred Heart). It was the order's first school in the Cleveland area, where they had been encouraged to establish one by a number of area women who had been educated by the Madams. Established in a building adjacent to GILMOUR ACADEMY in GATES MILLS, the school was not designed to be a traditional Catholic girls' school. Although religious instruction was important, an ecumenical approach was taken in which the religious-studies program was guided by not only a Catholic priest but also a Protestant minister and a Jewish rabbi. Nor was the school's pedagogy traditional. Team-teaching, the open classroom, interdisciplinary studies, and nongraded evaluations were foundations of the school. Education was coordinated with Gilmour, with shared facilities and faculty.
The Madams of the Sacred Heart remained at Glen Oak until 1972, when an Episcopalian minister, Rev. Lloyd Gesner, was appointed headmaster. He directed the school until 1977, when the URSULINE SISTERS OF CLEVELAND, long associated with education in the Cleveland area, were asked by the Board of Trustees to take over the school. Sister Claudia Klyn was appointed director, under whom a merger with Gilmour Academy was finalized in time for the 1982-83 school year.