Background: Students form interpersonal and intrapersonal classroom social experiences with peers. While diverse intervention programmes have been developed, few have integrated social-emotional learning into academic activities to maximize the potential for learning and development. Aims: This study examined the effects of collaborative small-group discussions on students' classroom social experiences at the interpersonal and intrapersonal levels. Sample: The study included 250 students (M[subscript age] = 10.98, female = 52%) and six teachers from 12 English language arts fifth-grade classrooms in two public schools in the United States. Methods: Students were assigned to one of three conditions: Collaborative Social Reasoning (CSR), Read-Aloud (RA), or Regular Instruction (RI). Students in the CSR condition participated in recurrent collaborative small-group discussions about stories related to complex social-moral issues, including friendship, social exclusion, ethics of care, and responsibility. Students in the RA condition read the same stories without discussions. Results: Collaborative Social Reasoning students were more socially accepted by peers and were less aggressive to others compared to students in the other conditions. RA students revealed more aggressive behaviour than other groups. In a post-intervention interview, CSR students reported improved communication and group work strategies, ability to maintain harmonious relationships, and class participation. A higher proportion of CSR students in the CSR than the other conditions reported experiencing positive change in classroom relationships. Teacher interviews were used in conjunction with student interviews to triangulate conclusions from qualitative interview data. Conclusion: Findings suggest effective ways to structure collaborative small-group discussions to foster positive classroom social experiences with peers.