The study used activity systems analysis to characterize the processes, dynamics, and tensions in the social practices developed by a class of academic low-achievers in a knowledge-building environment augmented by analytics-supported reflective assessment. A class of 37 Grade 9 low-achievers and an experienced teacher participated this study. Classroom data sources including classroom videos and observations, student artifacts, student interviews, and videos of reflective-assessment sessions were collected and analyzed. The findings indicated that staging tasks, frequent and opportunistic knowledge-building talks, the framing of discourse improvement as collective responsibility, and the acquisition of new skills and interests served as new tools mediating the students' activities. Our findings have important implications for the design of technology-rich environments as metacognitive tools to support low achievers. [For the complete proceedings, see ED601080.]