St Mary’s Convent, Ballyroan, formerly the home of Sr Mary of the Sacred Heart McCabe, whose family had gifted their home and lands to the Mercy Sisters in 1932, was established as a school by the Sisters of Mercy in 1960.  Initially, the Sisters used the house as a holiday home for business girls but by 1942 tuberculosis was prevalent in Ireland and the house was converted into a preventorium for the treatment of children who were at risk of contracting the disease.

By 1959 tuberculosis was under control but a new need had arisen in this beautiful area of South Dublin, i.e. education. The population was growing rapidly and on the 8th September 1960 the Mercy Sisters first opened the doors of Sancta Maria College as a Boarding, Senior Day and Junior Private School.  There were 23 boarders and 12 day girls in the Senior School and 35 children, boys and girls in the Junior School.  In the Senior School there was a staff of four, three Mercy Sisters, Sr. Loreto, Sr. Paul and Sr. Bernadette and one lay teacher, Mrs Gibney, and in the Junior School a staff of three, Sr. Marian Agnes, Sr. Regina Assumpta and Sr. Dolores.

From such humble beginnings, admirable progress was made and so, today, the College has an enrolment of over 580 students and a staff of 42 teachers.