Our Lady of Mercy School opened in 1925 and immediately eight of the ten classrooms were filled with over 325 students. By the following school year, the remaining two classrooms were also in use. The school provided instruction in both French and English with the number of classrooms equally divided between both languages.

Throughout the Depression, class attendance leveled off but by 1938, enrollment was once again on the rise and classroom space was limited. The board of trustees once again appealed to the Mond Nickel Company (now INCO) to assist in building an addition to the school. INCO refused but did offer the school space in the company's Nickel Club for two classrooms and a playroom.

Population growth in Coniston slowed throughout the 1940's and into the early 1950's, but by 1955, Our Lady of Mercy was once again in need of additional classroom space. This time, an addition of four classrooms were added to the south side of the separate school building and the space utilized in the Nickel Club was closed. By 1959, four more classrooms were added to the north side of the building. In 1962, Continuation School was closed and the separate school board re-purchased the building. One year later, in 1963, the first kindergarten class was started.

In the late 1960's, the separate school board introduced home economics, industrial arts, and music classes and created a gymnasium for the students. The board also made plans for the construction of a new school. The original brick structure of Our Lady of Mercy School was subsequently demolished and a new auditorium, offices, and classrooms were built between the north end and south end additions.

The new school was built across the street in 1969 and was styled almost identical to Our Lady of Mercy. It was named St. Paul the Apostle School. With the establishment of a second separate school, the trustees determined that Our Lady of Mercy would be utilized for French instruction while St. Paul the Apostle would be designated as an English school.

Today, École Notre-Dame De La Merci (Our Lady of Mercy School) and St. Paul the Apostle School continue to provide quality education to the Catholic children of Coniston.