St Stithians College was founded in 1953 and consisted at the time of the founding BP and BC classes. Planning for the girl's schools began in 1994. In 1995, the girls' schools started with grade 0 - grade 3 in the boys' prep buildings which now serve the Junior Prep under the name St Stithians Collegiate. The first senior girls were admitted to the Girls' College in 1996. In 2000 the names of the girls' schools were changed to Girls' College and Girls' Prep and the junior classes (Grade 0 - Grade 2) became part of the Junior Prep.

St Stithians College was founded in 1953 and consisted at the time of the founding BP and BC classes. In 1995, with the advent of the girls' schools on campus, the entities serving the boys became known as the Boys' College and Boys' Preparatory schools. Reference to the Boys' College within AtoM indicates the high school years from Grade 8 to Grade 12 for its entire history from 1953 to the present.