Ruth Langley had been joined in 1919 by Flora Templeton, who came as co-principal from Blair School, at St Georges Road, Toorak, with her students.

[1] In 1922 St Catherine's Grammar School had 80 students, and in need of more accommodation, Langley and Templeton purchased "Kilbride House", formerly known as "Beaulieu", at 17 Heyington Place, Toorak.

Flora Templeton died in 1931, but Ruth Langley continued the administration of the school, appointing Edna Holmes as headmistress.

[1][11] In 1942 World War II saw the school buildings requisitioned as a residence for the Women's Auxiliary Australian Air Force (WAAAF).

[13] St Catherine's School is located on a single 2.9 hectare campus, in suburban Toorak, 6 km south-east of the Melbourne city centre.

[15] On Sunday 3 July 2022, the St Catherine's 1st VIII made history by winning the Prince Philip Challenge Trophy for Junior Women's Eights at Henley Royal Regatta, beating Winter Park Crew, USA in the final.

Girls of all ages are encouraged to learn an instrument and to join the choirs, ensembles, orchestras and bands which rehearse and perform regularly.

From Year 9 onwards, music becomes an elective and VCE subject with emphases on developing performance, composition and analysis skills.

Individual tuition from specialist staff is available for violin, viola, cello, double bass, flute, clarinet, oboe, bassoon, alto saxophone, tenor saxophone, horn, trumpet, trombone, tuba, piano, harpsichord, recorder, classical singing, jazz singing, guitar, harp, percussion, music theory.