St. Mary Catholic School opened for the first time on September 6, 1949, with Sister M. Charlotte Goetze, Franciscan Sisters of the Sacred Heart, as the first principal. The enrollment totaled twenty-seven students in grades one through six.
On January 6, 1955, work was begun on a new church and school under the direction of the new pastor, Father Cecil Koop, OF.M. at the current location of 195th Street and 115th Avenue. The plans were for eight classrooms in the new school building. Within two years, seventh and eighth grades were added. During the sixteen years of Father Koop’s pastorate, the parish grew from 50 to 500 families.
In 1964, eight more classrooms and a second floor were added to accommodate the school’s growing enrollment. Both Mokena and the St. Mary Church communities continued to grow. St. Mary School had a waiting list in most grades, which showed the need for another addition.
Thanks to the generosity of parishioners, there was an eight million dollar parish center expansion in 2003. This addition brought a new gymnasium, cafeteria, music room, art room, science lab, and six new classrooms.
With this building expansion, plans to move from one section to two sections of each grade level began with two kindergartens. In 2008, the old 1956 church was converted into the Koop Library and Media Center, in addition to upgrades in the elementary wing of our school. Upgrades continued in 2012 with the conversion of unused space into smaller classrooms for small group instruction. Additional renovations were completed in 2017 to include a 3-year-old preschool classroom, an updated library, and a STEAM (Science, Technology, Engineering, Art, Mathematics) Lab.
Currently, St. Mary School has one 3-year-old preschool classroom, one 4-year-old preschool classroom, and two classrooms of kindergarten through grade eight with an enrollment of 450 students. St. Mary School continues its proud history as a faith-based educational ministry of St. Mary Catholic Church and an integral part of the parochial school system of the Diocese of Joliet. St. Mary School continues to provide spiritual development and educational excellence; “Preparing students for the future through spiritual and academic excellence”.