By 1945, the influx of young Catholic families meant a great increase of the number of school age children in the community. The parish community and the pastor, Fr. Robert Garvey, began planning the first parochial school in Bellevue.
A School Fund Drive was started in 1946 and each parish family was asked to contribute to the fund.
Leo Daly, architect for St. Mary's Church, was approached to design a school consisting of four classrooms, one of which was to be used as a chapel, a gymnasium/auditorium, a kitchen, and a convent; complete with living quarters for four sisters.
Costs for the project soared to a post-war high of $75,000, but with a $40,000 loan secured, ground for St. Mary's School was broken on September 14, 1947.
The lot the school was built on was an entire square block. The land for the school was donated by George Rushart.
Actual construction began in early 1948. (A mistake in the Title of Deeds Office created a need to obtain a waiver of building restrictions from fifty homeowners in the nearby Rushart Addition. Even though most of the homeowners were not members of the parish, they willingly signed the waiver and construction began in earnest.)
Various groups in the parish, including the Men's Club and the St. Mary's Altar Society worked to raise additional funds for the new school. One of the activities they set up was the Annual Lawn Social and Chicken Dinner, held for many years on the feast of the Assumption.
With the funding and building of the new school underway, Fr. Garvey visited the Motherhouse of the Dominican Sisters in Louisville, Kentucky, to arrange for a faculty for the school. The Reverend Mother agreed to send three Dominican Sisters - Sr. Rosalia, Sr. Irmina, and Sr. Joan Miriam. The sisters arrived in mid-August to prepare for the 96 students who had enrolled in the new school. The dedication took place on August 29, 1948.
By 1954, the enrollment of St. Mary's School had increased and the parish planned a four classroom addition, known as the Marian Addition.
The original church built in the 1920's was quickly becoming too small for a growing parish and by 1956, the cornerstone for the new St. Mary's Church was laid. The first Mass was offered in the new church on Palm Sunday, 1957. The shrine "Our Lady of the Runways" was donated by the Gerard Ianacone family and erected by the Kouba family in 1954.
The faculty of the school grew and in 1956, an addition was made to the convent to accommodate the increased number of Dominican sisters.
By 1959, Sr. Mary Cecile was principal and there were 450 students as well as 12 teachers, including eight (8) Dominican sisters. The pastor, Fr. Robert Garvey and his assistant Fr. Anthony Milone, taught religion to the students in grades 1 to 8. The 12 classrooms were spread around, with four classrooms in the original school building, four in the Marian Addition, one in the convent, two in St. Mark's Hall, and one in the church basement.
A new rectory for the priests was begun in September 1958, and completed by March 1959. In the summer of 1959, a large community room was added to the convent.
The parish and school grew rapidly and by 1960, there were 514 students enrolled. The student/teacher ratio was about 43 students to every teacher. With the increasing enrollment, new rooms had to be added. In 1962, the Pope John XXIII Addition, consisting of five new classrooms, the principal's office, library, teacher's lounge, and two storage facilities, was completed. This additional space allowed room for up to 750 students.
The 1960's and 1970's saw rapid changes in pastors and principals, along with the development of new programs for St. Mary's School.