The 1909 separate school board minutes read: “That a classroom be opened at 21 Main Street in East Toronto and be fitted up and equipped for school purposes...”, this opened by the Pastor Rev. George Williams. Classes began with 60 students and one teacher and a tradition began: that of teachers, lay and religious, in partnership with parents, devoting themselves to the spiritual and academic growth of their students.

• 1910 The school at 780 Kingston Road is opened.
• 1918 Sisters of St. Joseph join the school staff.
• 1949 Congregation of Notre Dame takes over with 350 students and Pastor Rev. Denis O'Connor is instrumental in having a larger facility built.
• 1952 Cardinal McGuigan officially opens new site.
• 1961 With 1,006 students, a new wing is added.
• 1968 With 1,300 students, a gymnasium and 12 classrooms complete the site.
• 1970s Enrollment declines, Notre Dame uses 3rd floor.
• 1984 St. John's celebrates 75 years.
• 1995 Joint funds, granted by Metropolitan Separate School Board (now the Toronto Catholic District School Board) and the city of Toronto, allow for renewal of the school yard.
• 2000 Corpus Christi Catholic School is consolidated with St. John.