St. Mary’s provides education under the ICSE/ISC board, New Delhi and is run by the Congregation of Christian Brothers of Ireland. SMO has classes from the Nursery section up to +2 level i.e. Clase XI and XII (Commerce section only). From the 2012 session admission of girls to the +2 level has started, breaking the school’s long-standing reputation of being a premier boys’ only school in Calcutta.