With a spectacular view of the Ottawa River across Brockhouse Way, Mackenzie Community School brings together the rich legacies of public schools in Deep River, so its history is a story of achievement, co-operation, a dedication to excellence, and the recognition of the need for communities to collaborate and celebrate diversity.

The building that houses MCS began as C.J. Mackenzie High School, named in honour of Chalmers Jack Mackenzie, a civil engineer educated at Dalhousie and Harvard. A recipient of the Military Cross and 21 honorary degrees, he was later president of the National Research Council, the first president of Atomic Energy of Canada Ltd. (AECL), and also president of the Atomic Energy Control Board. He was a football star in his college years, and an avid golfer, and one of the most important Canadians associated with the field of nuclear science at the time Mackenzie was built. Given that the town of Deep River was purpose built to house the scientists and employees of the nearby Chalk River Nuclear Laboratories (CRNL), it was fitting that the town's secondary school be named after Dr. Mackenzie.

But MCS is more than a secondary school, and so there is a wider story. In the early days of AECL, with the town of Deep River expanding by leaps and bounds, three elementary schools were built. Cockcroft Public School was built first, in 1946, and D.A. Keys Public School followed ten years later. Cockcroft was named after Sir John Cockcroft, a Nobel Prize winning physicist who was instrumental in the development of nuclear power. Keys was named for Dr. David A. Keys, a professor of Physics at McGill University and later Vice President of CRNL. A third school, T.W. Morison Public School, opened in 1961, and was named for Thomas Watt Morison, an administrator for Defence Industries Ltd., and first chairman of the Public School Board. Much has been written about these men and their impressive accomplishments, but equally remarkable were their leadership skills. Historian Wilfred Eggleston referred to T.W. Morison as "the founding father of the town", while the Ottawa Citizen wrote of Dr. Keys that he was "known for his ability to inspire confidence and command respect".

Mackenzie High School, meanwhile, was under almost constant renovation as it expanded to accommodate the burgeoning population of Deep River and the surrounding catchment area. In the 1960s, additional classrooms, a large library, a modern technical wing, a music room, two gymnasiums, a cafeteria and a 400-seat sloping floor auditorium were added. In 1976 an indoor heated pool was also built, the only facility between Ottawa and North Bay to fit certain requirements for swim competitions.

With expansion almost inevitably comes contraction, and declining enrolment necessitated combining the elementary population into T.W. Morison Public School, while the secondary students remained at Mackenzie. Eventually, the decision was taken to amalgamate the two schools into a single education centre, and the Mackenzie building was selected to become the first JK-12 public school in Renfrew County. Extensive renovations were made to the building and grounds, and public consultation over a name for the new facility took place. The choice was Mackenzie Community School, reflecting the strong association of the community with the tradition of science in their area, demonstrating a belief in the previous school's reputation for excellence in academics and sport, and the rich legacy of recognizing and celebrating our cultural diversity, and recognizing the strength and value of the community as a partner in education.

Mackenzie continues to respect and value its predecessors, and plaques on the walls recognize the Keys Hall, named in honour of Dr. D.A. Keys, the Cockcroft Science Wing, named after Dr. J. Cockcroft, and the Morison Library and learning commons, named for T.W. Morison.