You will, however, hear “the group is our church” in the church is model. This model is obviously on the same continuum as church of. But the church is model often differs in its theology of the nature and expression of church and in its intensity of small group emphasis.
The purpose for small groups in the church is paradigm is to be the church in its smallest form. This model sees small groups as the centerpiece of congregational life. Some advocates teach that “the church is the cell; the cell is the church.” They emphasize that evangelism, worship, communion, and Bible study all take place in the group.
Let’s face it. Regardless of the model you choose—church with, of, or is—your theology of the church will influence your decision. Some theologians believe a small group represents all the fullness of the bride of Christ. Others, however, would argue that small groups must be tied to a larger congregation for effective and accountable pastoral leadership, appropriate administration of the sacraments (even when observed at the small group level), sound biblical teaching, and church discipline.
Donahue, B., & Robinson, R., Willow Creek Association. (2009). The seven deadly sins of small group ministry. Grand Rapids, MI: Zondervan.