Today St Mary's Diocesan School is a Day and Boarding School for Year 9 to Year 13 Girls; it opened in1914. When it first opened there were two teachers - Miss Marchant, who was also the Principal, and Miss Shepherd - along with 2 boarders, 10 day girls and 10 day boys.

However it wasn‘t long before the school roll climbed and the school outgrew the buildings. The school board in 1917 purchased the current site of 11 and a half acres and arranged for new buildings to be built.

The building was named after Miss Marchant. Originally it provided accommodation, but with the building of the new hostels it is now used as teaching space.

In its early days the Principals of St Mary's were without doubt women of education, vision and courage. It is on foundations left by these women that St Mary's is built.

The building of the current chapel by Miss Roberton is one illustration of the qualities of these Principals. Miss Roberton, when she asked for a chapel to be built, was told there was no money - and to build it herself. What else was she to do but to do just that! Once the plans were draw up it was all hands to work. Staff, students and others were all pressed into digging and laying the foundations, making bricks and fundraising. With this kind of determination it was not surprising that the chapel was opened in 1956.