The school that was to become St Patrick’s was founded in 1956 as a coordinated effort among many stakeholders – lay, vowed religious, and clergy. It began as an initiative of the parishioners of Our Lady of Lourdes Parish (St Patrick’s Parish since 1960), led by pastor Father Michael McNamara, and involving great contributions from its School Building Committee – chaired by C.N. Montague, a fund-raising committee – led by Des Hoban, the Men’s Society, and Catholic Women’s League. The architect was parishioner John Di Castri, whose original design was a four-room school, and it was built by contractor E.J. Hunter and Sons. The Men’s Society took charge of preparing the grounds, building a bridge across Bowker Creek, and laying a water supply line beneath it. The Catholic Women’s League provided all the school’s student desks and was instrumental in remodeling a house next door to the school as a teachers’ residence for the Sisters of St Ann.
The school opened on 12 January 1956 at a temporary location in the parish hall on Haultain Street with 35 students registered in grades 1-4 during its first two terms. It moved to its current location in late Spring 1956, and in Fall 1956, its first full year of operation, it had 197 pupils enrolled in a building intended to accommodate 200 students. By 1958 it had registered almost 300 students in grades 1-6, which required again using the parish hall – this time to accommodate its grades 5 and 6 classes – and leading Fr McNamara to announce plans for building 6 new classrooms and a gymnasium. Its initial name was Trent Street School, as the parish was still named Our Lady of Lourdes, but the name St Patrick’s School was in use by 1957.

The Sisters of St Ann staffed the school at its founding, and for 36 years until 1992. Sisters Mary Mercy and Mary Eugenia taught Grades 1-4, and Sister Mary Edmunda was the first principal. Sister Mildred Lynch succeeded her in 1961, and in 1965 Sister Norah Keane was appointed principal and held that position for 14 years. For the first year and a half the sisters commuted daily from St Ann’s Academy, until completion of the teachers’ residence in Summer 1957, where they lived until 1991. The teachers’ residence was then demolished to make room for an addition to the school. Sister Eileen Curteis was the last Sister of St Ann assigned to St Patrick’s school, and her assignment there ended in 1992.

The gymnasium was added to the facilities in 1961. In 1962 the school accepted students up to Grade 9, with the enrolment then being approximately 450 students. During 1991-92 the new wing which houses the Kindergarten class, Grades 1 and 2, Computer Room and the Student Support Room was opened. There were 380 students registered in 1992. During 1993-94, a renovation to the 1956 wing provided refurbished classrooms, the library, and a new administration area complete with an infirmary and staff room. In 2006, a new music hall and primary playing field were constructed. A major renovation in 2016 seismically upgraded the original 1956 wing, including the installation of an Early-Warning System and Earthquake-proof desks in its classrooms. Finally, in 2018 the primary field surface was upgraded to an artificial turf. The 2019 enrolment is 320 students.

The school has received partial provincial government aid since 1977, with the passing of the Independent Schools Act, when the school came under the auspices of the Ministry of Education.