When the Sisters of Mercy first arrived in Auckland, they were worried that there was no Catholic school in Devonport. There was just a little wooden Church on the side of a hill. So, Sisters would travel by boat to Devonport every Sunday to meet with the Catholic children and teach them about God. The Sisters sometimes travelled by ferry, but other times they had to travel by row boat to reach Devonport.

The Sisters soon decided that they needed to set up a Catholic school for the children. In 1896 they bought a small house opposite the Church and made it their convent. The first Sisters to live in Devonport were Sr Peter Byrne, Sr Columba Prendergast and Sr Stanislaus Carmody. On the first day of the new school there were 70 children.

In the beginning there was no school building, so the Sisters used a room in the convent and the Church as classrooms.

After teaching during the day, the Sisters taught children music and painting to earn some money to help build new proper classrooms.

A new school was finally built in 1897 and the Sisters called it St Leo’s School. It was named after St Leo’s Convent in Ireland, which was the Sisters home in Ireland before they had come to live in New Zealand.