In 1906 a combined Elementary and High School for students in the Grimsby area was built on Livingston Avenue . When it became overcrowded, land was purchased for a new building. On May 20, 1926 200 students entered the newly built Grimsby High School on Boulton Ave. The building comprised an auditorium that seated 450, a basement gym, 1 lab, 2 business classrooms, an art room and 5 other classrooms. There were only 6 staff members plus a teaching principal in the beginning, and music instruction did not begin at this school until three years later, in 1929.
By 1955, the student population had grown to 445 so an expansion was completed which added 6 more classrooms and another lab. In 1957 phase 2 of this expansion was completed with 2 more classrooms, another washroom and a locker room added.
A vocational wing was added between 1961 and 1964. Another gym, a Home Economics room, Industrial Arts shops and a new cafeteria were built, plus 2 staff rooms, 7 classrooms, another Lab, and a music room.
The last addition to this building was completed in 1967. A large wing was added at the east end of the school that included the new Library.