St. Mary's School was established in 1972. It was an Episcopal school, housed in St. Mary's Church, but privately owned. When the private owner, Mrs. Kitty Warren decided to discontinue the Edmond school, she offered it to St. Mary's Church. In March of 1977, the Vestry of St. Mary's Church voted to continue the school as a parish day school, and St. Mary's School became an official entity of St. Mary's Church of Edmond, Oklahoma. The school was housed in the old St. Mary's mission church building, which was later referred to as the Canterbury House.
In the fall of 1977, there were 20 preschoolers and 10 kindergartners who attended classes in the mornings. By the fall of 1980, early childhood programs were expanded and enrollment grew to 50 children. A Spanish program was implemented at this time.
In 1983, the church added an education wing to the existing building. That fall, the school opened with 100 students and with a faculty that also doubled in size. The classes consisted of a morning and an afternoon session of three-year-old preschool, four-year-old preschool, and kindergarten. In the fall of 1988, the Canterbury House was reopened to house an additional class of four-year-old preschool students, bringing the enrollment to 112.
In December of 1988, property adjacent to the church property was purchased, and plans were made to expand the school further. The Canterbury House and the newly purchased "Burton House" underwent minor remodeling to accommodate this expansion. In the fall of 1989, the morning kindergarten was expanded to become an all day kindergarten program, meeting in the Canterbury House; and the Burton House became home to a first grade class and administrative offices. At the same time, an additional class of three-year-old preschool students and special classes in music and physical education were added. Enrollment for the 1989-90 school year was 143, with a faculty and staff of 17.
At the closing of the 1990 school year, Susan Radke, school Director for 15 years moved back to her home state of Iowa. Nancy Hetherington was appointed as the new Director of St. Mary's School.
During the summer of 1991, St., Mary's School underwent further expansion with the acquisition and renovation of the property just west of the playground, located at 312 East Main Street. The front half of the lower floor was remodeled to accommodate our first second grade classroom. The opening of 1991-92 school year saw enrollment at 153 with 18 faculty and staff members. During the summer months of 1992 the back half of the house was renovated to add a third grade center to open in the fall. The 1992-93 school year opened with 148 students and 20 staff members.
During the 1992-93 school year St. Mary’s School entered into the accreditation process with the Southwest Association of Episcopal Schools. This process recommended by-law changes, which lead to the naming of the school director as Head of School and the Rector of St. Mary's Church as School Chaplain. It was also voted by the School Board of Directors to seek separate incorporation status for the school and to expand St. Mary's School to include a full elementary program (first through fifth grade). Fourth grade opened the fall of l993 and fifth grade the fall of 1994. A classroom center just west of 312 Main Street was built during the summer of 1993 to house elementary grades. Eleven fifth graders participated in the first fifth grade graduation ceremony for St. Mary's Episcopal School on May 31, 1995.
On July 31, 1995, The Canterbury House was destroyed by fire. A new structure was built which connected to the south end of the classroom center. During mid-October 1996, the all day kindergarten programs moved into their new classrooms. St. Mary's School received a $300,000.00 grant from the Diocese of Oklahoma toward the construction of a new education building in the fall of 1996. Together with St. Mary's Church, necessary funding (1.4 million) was raised to build a two-story education building. January 18, 1997, St. Mary's School moved its elementary classes, administrative offices, its computer lab and media center into the new education building which served the church and school for educational outreach.
In the summer of 2000, the school added an additional modular classroom center to accommodate the opening of two first and second grades. In the spring of 2001, the School Board of Directors purchased a 51-acre track of land on Covell for the purpose of building a facility to house upper elementary grades and for expansion of Middle School. Funds raised through the Building our Future campaign resulted in the construction on this facility which began the summer of 2003. Phase 1 opened fall 2004 housing third – fifth grades and administrative personnel. Through additional fund raising efforts, a vacating agreement with St. Mary’s Church and a $500,000 grant from the Diocese of Oklahoma, Phase 11 was completed in the late spring of 2006 giving the school a complete 23,000 square foot facility. The remainder of the school moved to this new location during the summer of 2006. Today, the official location for St. Mary's Episcopal School is 505 East Covell Road.
The outdoor environment has been enhanced to include hiking trails, re-developed ponds with observation dock, a bird blind and observation area, an outdoor chapel setting, a little league baseball field, MJ Field (given as a memorial gift for Mitchell Jones on behalf of the Jones/Morgan family), and an outdoor classroom.
With the retirement of Nancy Hetherington in May of 2013, Pamela Dockter joined the St. Mary's family as Head of School as only the third Head in the school's 36-year history.