The first attempt to form an Old Boys' Association was made in 1926 but it only survived one year. A more determined effort was made in 1950 by Headmaster Jacob Morgan and his staff. Initially the committee consisted of former pupils but the secretaries came from the school staff. After the reorganisation of secondary education in 1971, the Association was run entirely by Old Boys.
The Jubilee anniversary of the formation of the Association was celebrated in 2010 with a joint concert with the High School the evening before the reunion dinner.
Some historical information about the Cradoc Road School can be found in an article by Clifford Carr on the Powys Digital History Project website here. The Penlan School is also mentioned but it only lasted 13 years before the switch to comprehensive education.
In 2023 the constitution of the Old Boys' Association was changed to include former pupils of the Girls' Grammar School and the Association's name was changed to Brecon Grammar Schools' Association (BGSA).