This study investigates designs for developing knowledge building (KB) and higher order competencies among academically low-achieving students. Thirty-seven low-achieving students from a ninth-grade visual arts course in Hong Kong participated. The design involved principle-based KB pedagogy, with students writing on Knowledge Forum® (KF), enriched by analytics-supported reflective assessment. Analysis of the discourse on KF showed that the low achievers were able to engage in productive discourse, with evidence of metacognitive, collaborative, and epistemic inquiry. Analysis illustrates how the design supported student engagement, including (1) reflective inquiry and social metacognition; (2) reflective meta- and epistemic talk; (3) evidence-based reflection for collective growth; and (4) reflection embedded in community ethos. Implications of reflective assessment for supporting low achievers for inquiry learning and KB are discussed.