St. Mary Parish conceived the idea for a Parish School in 1943 and began a school fund to bring the idea to reality. The idea remained just that, an idea, until 1953 when the two-story parish house was demolished to make room for the present day school building. The cornerstone was laid on November 28, 1954, by the Most Reverend Albert R. Zuroweste, Bishop of Belleville. The building was completed within the next year and school opened on Monday, October 3, 1955. The school was staffed by four Sisters of the St. Francis of Mary Immaculate of Joliet, IL, one of whom served as the Principal/Teacher. The principal assisted Monsignor Burke in the management of the school. The school continued to grow from its original enrollment of 168 students to 235 in 1966 when it became necessary to close the doors due to a shortage of sisters. During the eleven years of operation, Monsignor Burke maintained governance of the school's operation and finances assisted by the principal. The St. Mary Home and School Association was formed and was active from the inception of the school in 1955. Their activities were limited to fund raising events at the time. A total Parish Board of Education was formed in the 1980's; however, its tasks were not clearly defined and it was disbanded after a period of time due to lack of interest.

After a two year period St. Mary School reopened its doors in 1968 again under the direction of Monsignor Burke. The faculty consisted of two Sisters from the St. Francis of the Providence of God Order from Pittsburgh, PA, and two trained teachers. Again, one of the Sisters, Sister Amy, served as the principal in addition to her teaching duties. The four teachers each taught two grade levels as had been done during the first 11 years of operation.

Father Melvin Vandeloo became the Pastor of St. Mary Parish in 1983 and assumed the duties of managing the school. In 1986, St. Mary School saw a change in the administrative structure in the hiring of Sr. Helen Sirvinskas as full-time principal. The management and budget of the school became the duty of the principal; however, the Pastor would have final authority.

Father Dan Jurek became the Pastor in July 2000 and assumed responsibility for the school. In 1993 the St. Mary Parish Council appointed the first St. Mary School Board of Education.

Father John Iffert was first appointed as Administrator of St. Mary Parish by Most Reverend Bishop Edward Braxton in July 2008, and was then appointed Pastor of St. Mary Parish in July 2010.

According to Diocesan guidelines, the school board became a consultative board which sets policy in accordance with the diocesan standards, but does not get involved with day to day management of the school. The board performs many of its duties through the committee system. The committees of the board are: Finance, Ownership/Governance, Enrollment/Development, Facilities, School & the Community, and Development/Public Relations.

Sr. Helen Sirvinskas retired as principal in 1996 and was replaced with the school's first trained principal, Ms. Sue Cunningham who served from 1996-2005. Brett Heinzman was hired in 2005 and currently serves as Principal of St. Mary School. Mr. Heinzman manages day to day operations, budget, staffing, and assists with fundraising. Currently the St. Mary School Board meets monthly to set policy and assist the principal with school needs. Both the St. Mary School Board and principal work in conjunction with Very Reverend Father John Iffert who has the ultimate management authority.

In 1998 a long planning process was recognized and implemented for the future development of St. Mary School.

The original St. Mary School Board was given orientation from Tom Posnanski Director of the Office Education for the Diocese of Belleville. Annual school board training is offered to new members by the Office of Education in Belleville. Currently, policy and procedures are implemented through St. Mary School Board recommendations while adhering to the guidelines set forth by the Diocese of Belleville. St. Mary School Board is the policy making body of the school. The school board works with the principal to create policies, which meet the needs of the students and promotes the Catholic values of St. Mary School. The school board also helps create plans for future improvement and growth of the school. The school board has input hiring the principal and participates in the yearly evaluation of the administrator. The school board is compiled of members elected by school parents and parishioners of St. Mary Parish. The Pastor, St. Mary School Board President, and St. Mary School Principal serve as ex officio members of the board.

The principal is responsible for evaluating all school staff members. Mr. Heinzman uses 3 types of evaluations annually with all teachers. Walk-through Evaluations are a 10-15 minute instrument that is used subjectively at the principal's discretion for “spot checks”. Formative Evaluations, both scheduled and unscheduled are used to critique lesson plans, classroom management skills, time management and overall job performance. Finally, Summative Evaluations are reviews used for overall evaluation of the staff. The Principal completes a minimum of 1 of each of the three types of evaluation on all teachers every year. The principal then compiles the teacher evaluation data and delivers a report to the school board. Based on performance, teachers are the offered or not offered an annual teaching contract.

The principal is evaluated through an annual form created by the Diocese of Belleville. Each school board member is given one month to complete the checklist and return his/her form to the Pastor. Similarly each staff member is given a Diocesan created evaluation form to complete regarding the principal's performance. These evaluations are then returned to the Pastor. Ultimately, it's the Pastor's responsibility to critique the principal's job performance.

The Pastor has ultimate governance of the school.