The Caerphilly Secondary School for mixed sexes was divided in 1929 and replaced by Caerffili/Caerphilly Boys' Secondary School in this new building on Mountain Road. The Girls' Secondary School remained at Crescent Road. Caerphilly Boys' School was effectively an Intermediate or 'Grammar' School and extended its curriculum to include traditional Grammar School subjects such as Latin and French. Its wider vocational function developed further when pupils of the Junior Technical School were added in 1953.The change in status was formally recognised in 1953 when it became Caerffili Boys' Secondary Grammar Technical School. The Junior Technical School opened in 1930 in the building constructed for the Mining and Technical Institute in 1927. Caerffili Boys' and Girls' Schools were amalgamated in 1974 to form St Martin's Comprehensive School, Hillside, Mountain Road.

Reference: Glamorgan Archives: Caerphilly/Caerphili Boys Secondary School and St. Martins Comprehensive school, Caerphilly records 1927-1989: Administrative and biographical history. Ref:GB 0214 D375.