The goal of this study is to examine the influence of a collaborative small-group discussion approach on students' social self-efficacy and class relationships. This approach, called Collaborative Social Reasoning (CSR), was informed by the substantial literature on Collaborative Reasoning (Chinn, Anderson, & Waggoner, 2001) and social-cognitive development theories. A total of 120 fifth-grade students from three low-achieving and two high-achieving fifth-grade classrooms in a suburban school of a Midwest city participated in the study. The current findings suggest that CSR effectively improved low-achieving students' social self-efficacy and buffered against the declining trend of class relationships. High-achieving students were less influenced by CSR. The differential effect of CSR will be further examined and discussed in the future.