Selwyn House School, originally called Lucas School, was founded in Montreal in 1908 by Lieutenant Algernon Lucas, a graduate of Selwyn College, University of Cambridge. With funding provided by Sir Herbert Holt—the future president of the Montreal Heat, Light and Power Company—Lucas and his friend L. St. George installed Lucas School in a building on Crescent Street. After two years, the student population grew, necessitating a move to a new building at 452 (later 1538) Mackay Street. The school remained in that location until 1930, except for several weeks in the winter of 1914-15, when drainage issues on Mackay Street prompted a temporary relocation to the hall of the Church of the Messiah on Simpson Street.
In 1912, Algernon Lucas transferred the ownership of Lucas School to Colin Campbell Macauley, a former colleague from Selwyn College. As the new headmaster, Macaulay renamed the school to Selwyn House in honour of Lucas and Macaulay’s shared alma mater. In 1920, the school was divided into the junior and senior schools; the senior school remained at Mackay Street, while the junior school was moved to 711 Sherbrooke Street. At this time, the naming of forms was implemented, with forms A to D in Junior School and forms I to VI in Senior School. Later in the decade, two more forms were added to the Senior School. After the initial split, the school was administered as a single unit, and staff commuted between the junior and senior schools. By 1926, the schools and their staff were officially separated, with Macaulay acting as the headmaster of the junior school on Sherbrooke Street, and Geoffrey Wanstall becoming the headmaster of the senior school on Mackay Street.
When Macauley retired in 1929, he transferred the ownership of Selwyn House to Geoffrey Wanstall. The following year, Wanstall joined together the junior and senior schools at a new location on Redpath Street—a larger building which was gradually expanded to house a library, a gymnasium, a dining room, and an assembly hall. On May 7, 1945, Wanstall died unexpectedly of influenza; having left no will, the future of the school’s governance was uncertain. In response to this crisis, a group of Old Boys formed an organizing committee that sought to incorporate Selwyn House as a non-profit organization called the Selwyn House Association. Justice G. Miller Hyde served a significant role in this process, including the selection of Robert Speirs—the then Assistant Headmaster of Lower Canada College—as the new headmaster of Selwyn House. A Board of Directors was established to oversee the non-profit, the first chairman being G. Miller Hyde.
In 1961, the directors of the Selwyn House Association purchased the former site of Westmount High School (95 Cote St. Antoine), relocating Selwyn House to the new building. Many expansions to the premises were made throughout the decades, including the purchase of the St. Andrew’s United Church (now the Macauley Building) in 1985, and the construction of the Speirs Building in 2002-3. In 2023, Selwyn House began offering a Pre-University year (Grade 12) in addition to its existing Kindergarten to Grade 11. Today, the school operates as a non-government-subsidized independent boys’ school, with approximately 130 faculty and staff serving 600 students from K-12.