The Catechesis of the Good Shepherd (CGS) is a Montessori-based religious formation program for children beginning at the age of three. It seeks to create and facilitate a sacred, "hands-on" space for children called an Atrium in which both the children and the catechists can hear, ponder, and celebrate the most essential mysteries of the Christian faith as revealed in the scriptures and the liturgy.

CGS was developed in Rome by Dr. Sofia Cavalletti, a Biblical scholar, and Gianna Gobbi, a Montessori-trained educator. Cavelletti and Gobbi recognized that there is an existing relationship between God and the child. The child is already wondering about God and God is already loving the child. The CGS atrium is a space prepared specially for the child, in which the child's relationship with God is given time and space to grow.

St. Maria Goretti Catholic School has a Level 1 Atrium for children in PreK-1st grade. Children in the Level 1 Atrium work with materials and experience presentations on the life of Christ and His teachings to help make the great mystery of who God is more understandable. They ponder Jesus as a real person, who walked the earth in a specific time and in a specific place. They explore the article and gestures of the Mass as well as the sacraments of Baptism and Eucharist. They mark the passage of time in the liturgical year through prayer, song, and celebration.