The school became a full high school in 1925, and was subsequently renamed Canterbury Boys' High School. For some years, difficulty was experienced in encouraging boys to complete 4th Year, and to sit for the Leaving Certificate Examination the following year. This was due in part to the difficult economic conditions of the time, and in other cases, boys preferred to enrol in one of the more established high schools such as Sydney Boys' High School and the Sydney Technical High School. In order to increase enrolments in 4th year, Rourke pressured the Department, and boundary lines were established so that boys living within the area were compelled to enrol at Canterbury. The school was to later become a selective high school from which time many student enrolments were from out of area.