The roots of the Congregation began in LePuy, France, when the Sisters of St. Joseph was established in 1648 by a French Jesuit named Jean Paul Médaille.

[2] When the Ontario government purchased the convent property to construct four office towers, the Sisters of St. Joseph relocated the College School across the street at its present location.

On May 31, 2012, the head janitor of SJCS, Vincent Perna, was charged with attempted murder as police alleged Perna went to the staff room and tried to help kitchen staff light a stove after a gas line had been severed in the basement of the school.

[3] St. Joseph's College School offers a full-time Extended French program, a variety of Advanced Placement and enriched courses, and a wide range of classes in the sciences and the humanities.

St. Joseph's regularly scores within the top 10% of schools on the Education Quality and Accountability Office's standardised tests.

The Chaplaincy program at St. Joseph's College School provides all staff and students experiences of prayer, the sacraments, social action and Catholic leadership.