St. Mary's High School is one of the oldest schools in Secunderabad. It was established in 1885 and is managed by the Hyderabad Archdiocese Educational Society (HAES). Fr. Valentino Bigi was the first Principal of the school. The school is run by the Roman Catholic Order. The school formerly admitted only boys but has become co-educational. The school has four houses which are named after the first Four Principals of the School - Bigi (Yellow), Marian (Blue), Vas (Red) and Fernandez (Green). Though the school is Catholic Minority Institution, admissions are open for all students irrespective of caste, creed and religion.