The school was established on 6 May 1861, began with just three students, and officially registered as a high school in 1867. Its founder was Reverend Joseph A. Willy of the
Society of Jesus (the "Jesuits"), who controlled the school until June 1935. It was then taken over by the
Franciscan order until 6 October 1950. Since 1950, it has had Pakistani principals belonging to the Roman Catholic Archdiocese of Karachi. Fr Stephen Raymond, a diocesan priest, became the first Pakistani principal of his alma mater in 1950. The era of Fr Raymond as principal from 1950 to 1974 is referred by many old students as the "golden era" of St Patrick's. Fr Raymond is credited with constructing the Cambridge Building (1950), St Patrick's College (1952), the Teachers' Training College (1959), the first School Auditorium (1972). The school celebrated its centenary in 1962 with the President of Pakistan, Field Marshal
Mohammad Ayub Khan as the Chief Guest. St Patrick's High School was one of the few private educational institutes that escaped nationalization in 1972. On 6 May 2011, the former students of the school instituted the Father Stephen Raymond Gold Medal to be awarded to the top student from the Commerce Section, as part of the 150th anniversary of the school. == Former principals ==