The PSA was formed in 1905 by the Headmasters of Christian Brothers College, Guildford Grammar School, Perth High School and Scotch College. Wesley College was admitted in December 1951, Christ Church Grammar School in October 1956 and Trinity College in 1968.
Perth High School was renamed Hale School in December 1929. In 1938 the boarders and some day students from CBC moved to Mount Henry to commence Aquinas College. The College colours and membership of the PSA were also transferred to Aquinas College.
CBC continued with the remaining day students. In 1962 CBC moved to the East Perth site and was re-named Trinity College.