In 1938, at the request of Archbishop Joseph Cantwell of Los Angeles, the Sisters of St. Francis accepted the responsibility of staffing the new parish school being built in Santa Maria, a small agricultural town with a population of approximately 8,000. When the four teaching sisters arrived with one housekeeper, the pastor,
Reverend Thomas Murphy, graciously welcomed them. The sisters were introduced to their temporary home, the rectory. Because the convent was not quite ready for occupancy, Father Murphy and his assistant, Father Vandenberg, moved to the Santa Maria Inn.
On September 14, 1938, after Mass in honor of the Holy Spirit, St. Mary's School was officially opened with an enrollment of 59 students in four classrooms, two grades in each room. On Sunday, October 2, 1938, Archbishop Cantwell, in the presence of a large number of adults and the school children in their new uniforms, blessed the school building, the crucifixes for the classrooms and the United States flag, which was then raised and saluted with proper ceremonies. Although their classes were small, the sisters were very busy indeed, initiating the children into the traditions of Catholic school life. They celebrated all feasts, religious and secular, with great enthusiasm. They formed a children's choir, taught music lessons, practiced procession for Forty Hours, May Crowning, and Corpus Christi. They prepared the children for their First Confession, First Holy Communion, and for Confirmation. Besides teaching Catechism to the children of the parish who were not attending St. Mary's School, they went on Saturdays and Sundays to the parish churches in Guadalupe and Los Alamos to teach the children there. The first school year closed on the Feast of the Sacred Heart, June 16, 1939, with solemn graduation exercises for three boys and three girls in the parish church.
In September 1939, 104 children were enrolled. So gradually did the school population increase that all children were accommodated in four classrooms until 1948 when four new classrooms were added. That year brought several improvements: the field across from Cypress Street was fenced in and became the main playground; the new public address system proved a special blessing for as yet there was no hall in which to hold school assemblies. As Santa Maria grew, so did St. Mary's parish and school. In 1958, the new church was built. During the years 1963-1964, eight additional classrooms were built and in 1965 the Parish Hall was added on the sight of the previous church building. School population continued to grow until 1971, when for many reasons, among them the erection of another parish and school in the city, the number of children decreased and one of the first grade classes was eliminated. In each succeeding year, a class was dropped until eight classes remained, 1st-8th grade. 1985 saw the addition of a kindergarten class.
St. Mary's celebrated its 50th year of service in the field of education in 1988. The year was filled with various activities, among which was the donation of the mosaic of St. Mary of the Assumption by the alumni and loyal friends. It adorns the front of the school building. The last of the Franciscan sisters moved away in June of 1998 after serving the school faithfully for 60 years. The first lay principal was then appointed. On November 1, 1999, the Feast of All Soul's Day, a preschool opened in the vacated convent. Since its inception, the preschool has been filled to capacity and is a great feeder to the elementary school.