<![CDATA[This study aimed to describe the conceptual understanding of high-, medium-, and low-ability students in Discovery learning based on graduated scaffolding on the topic of future value of annuities (prenumerando and postnumerando). The study employed a descriptive qualitative approach within a Lesson study framework conducted through two cycles (plan–do–see) involving eleventh-grade students at SMA Negeri 3 Malang. Deep analysis was applied to three subjects selected through purposive sampling based on the results of the diagnostic assessment. These three subjects represented three student ability groups: high (10 students), moderate (17 students), and low (8 students).Data were collected through diagnostic assessment, differentiated student worksheets, observations, documentation, and analysis of students’ work. The findings revealed that students’ conceptual understanding varied according to their learning readiness. High-ability students demonstrated flexible deductive–inductive thinking patterns, independently derived formulas, and accurately applied concepts to contextual problems. Medium-ability students showed guided linear thinking patterns through gradual scaffolding, whereas low-ability students exhibited fragmented thinking patterns with a higher dependence on teacher support. The Lesson study results indicated that Cycle 1, which implemented random grouping, was unable to optimally accommodate the diversity of students’ learning readiness, as reflected in uneven participation and the emergence of conceptual errors. Improvements implemented in Cycle 2 through the use of diagnostic assessment, readiness-based grouping, and graduated scaffolding-based worksheets resulted in more equitable student engagement and enhanced conceptual understanding. The findings emphasize that students cannot be treated uniformly. Effective mathematics instruction requires learning-readiness-based differentiation to create more adaptive, meaningful, and inclusive learning experiences that accommodate students’ diverse needs.]]>
