Mount Slesse Middle School was designed and constructed in 1996 and built according to the Middle School Philosophy. Originally, the school was home to grades 7, 8, and 9.

From the beginning, families were encouraged to be involved in the development of the school. In the winter of 1996, parents from surrounding elementary schools were informed about the Middle School Philosophy and meetings were held to establish priorities for "their school."  On March 6, 1996 the first Parent Advisory Committee was held to begin working on the school's Mission Statement. Today, our mission statement embodies that work and honours our whole wolf family.

Students were also involved from the beginning. Each new class was asked to select school colours, a school name, and a school mascot. In the end, a timberwolf was the most popular choice and the school colours were established. Today, those colours are green, silver and black.

In 2018, our school district went through a reconfiguration and in September of 2018, MSMS saw a new intake of grade 6 classes with grade 9 students moving up to secondary school. Today, MSMS proudly serves grade 6, 7, and 8 students who live and learn on the traditional, unceded and ancestral territories of the Stó:lō people.