Fr Maurice Carroll, Parish priest of St Brendan’s, invited the Sisters from the Ascot Vale community to go down to Kensington each Sunday from 1910 to 1915 to give religious instructions. In 1916 Fr Aeneas Hennessy erected what is now the parish hall in Gower Street. It was divided into three classrooms. Fr Bride took over in 1919, and made plans for the building of a new school building. Senior grades were added in 1921 and 1922. In 1927 Fr O’Farrell built a two storied senior school.

The post war migration boom, the building of the Housing Commission Flats in the late 1960’s and the demolition of the Holland Park estate in the late 1990’s have had a big impact on the population of the school.

In 1971 thanks to the deep concern and the generosity of the Hardiman family and other parishioners, the old and dilapidated junior school was demolished and a modern new wing was built in 1971. An adventure play ground was added in 1972. In 1973 the school was classified as ‘disadvantaged’ and $20,000 was a granted for refurbishing and $71,000 for a new administrative wing. The hall was renovated and new furniture bought, so it could be used for indoor physical education The tuck shop area was renovated in 1975, new furnishing were obtained and all classrooms completed. One reason the school benefited over the decades was because of its use as a school for trainee teachers from the Mercy teachers College.

Many devoted sisters and lay staff have continued to build on the foundations of the early days at Holy Rosary.

Recent years have also seen rapid changes through a changing curriculum to meets the needs of the 21st century, refurbishment of all the administration, staff and learning areas of the school and the installation of new playgrounds. The changing demographics of Kensington have led to an increase in enrolments.