It was founded in 1926 by the Benedictine Sisters as a girls' school and junior college.[4] In the early 1960s, Monte Cassino terminated its boarding school, and its residence hall became the new home for the sisters of the St. Joseph Monastery.[5]
When the high school closed a preschool opened and the educational institute adopted co-education for its middle school. At the same time, the neighboring Catholic boys' school, Cascia Hall Preparatory School, began admitting girls in middle school and high school, effectively absorbing Monte Cassino's role as a girls' high school. (The two schools had shared some classes in previous years.)[6]