Runnymede Collegiate Institute (known as Runnymede CI, RCI, or Runnymede) first opened in 1927 and is operated by the Toronto District School Board. Prior to 1998, the school was part of the Board of Education for the City of York.
Runnymede Collegiate Institute was completed and officially opened on November 11, 1927, although classes had begun on September 6 for 250 students and a staff of 10 teachers led by Principal Bruce W. Clark. The original Collegiate Gothic building was designed by Charles Wellington Smith and consisted of eight classrooms, three science labs, an auditorium, a library, a gymnasium, a cafeteria and a locker area on three floors. Significant additions to the building were completed in 1928, 1958 and 1966. The building now includes over 30 classrooms, a swimming pool, two gyms, computers labs and a large cafeteria.
The school was built on land, which had belonged to John Scarlett. His is estate was called “Runnymede” after the field of Runnymede, where King John of England signed the Magna Carta. The school's colors, red and white, derive partly from Scarlett's name, and also from the fact that the school opened in the year of Canada's Diamond Jubilee. Owing to their red school jackets, Runnymede students came to be known as Redmen in the 1930s. Over time an Indian head logo was adopted to go with the name. The Redmen name and logo were retired in 1994.
Runnymede Collegiate Institute celebrated its 90th anniversary on Saturday, May 6, 2017. Hundreds of alumni, former teachers, and current students attended the reunion. There were "decade rooms" where former students from each decade would meet up with their classmates and teachers.