The beginnings of De Mazenod Separate School are found in the creation of the first separate school in Ottawa East. In 1900 the Catholic community of Ottawa East formed the new Parish of Ste. Famille (Holy Family) and in 1901 created the Ottawa East Roman Catholic School Board. By 1902 a new church and school had been built. There is much more on this story in the history of Holy Family School found here.

Initially both French and English Catholics worshipped and studied together in Ottawa East. At the end of the first decade of the Twentieth Century however, there was a growing demand for a separate institution for the teaching in the French language. It appears that an 'unofficial' school existed at this time for senior level French students that could not be accommodated at the Holy Family School. In 1915 fifty taxpayers in the area petitioned the provincial government for assistance in acquiring acceptable space for these classes. Little was done to attenuate the situation, as there was opposition to expansion of the separate system.

Finally in 1923, under the leadership of Trustee Beaudry, the Separate School Board acquired the property at the southwest corner of Main and Graham. Records indicate that the Oblates of Mary Immaculate had originally purchased the property from the Graham Estate and sold it to the school board for $38,000. The land included lots 28 to 40 on Reg. Plan 90280. The Grahams had called this land "Ardagh Square".

The school opened in the Graham home on Friday, November 9, 1923 with 60 students attending. The original suggestion for a name was St. Michel but the school board felt that the role of the Oblates in purchasing the land be recognized. As a result the school was named after Saint Eugene De Mazenod, the founder of the Oblate Order.

The school functioned in this location until 1933 when the contractor H. Dagenais built the new structure at the same location. It is not clear as to when the school ceased operation but the building has had a storied history over the past two decades with many different uses.

(Editor's Note: Unlike the other schools described in this history, there was very little information available about De Mazenod's history. Hopefully someone will fill this gap in the future.)