Cultural Values in the Classroom: The Role of the Nan Sakato Principle in Developing Mathematical Communication

This study developed a cooperative learning model integrating Numbered Heads Together (NHT) with the Minangkabau Nan Sakato principle to strengthen students’ mathematical communication. Using a research‑and‑ development design based on the Plomp development framework, the study involved 67 Grade 10 students from two public senior high schools in West Sumatra, Indonesia. The developed model was evaluated in terms of validity, practicality, and effectiveness through expert validation, classroom implementation, and mathematical communication assessment. The intervention was conducted over eight meetings, focusing initially on systems of linear equations in three variables and subsequently on related linear‑ inequality tasks to examine the consistency of communication practices. The results showed that the model met validity and practicality criteria and produced moderate improvements in students’ mathematical communication, with mean N‑gain scores of 0.47 and 0.44 across the two classes. Significant differences between pretest and posttest scores were also observed. Beyond demonstrating instructional effectiveness, the findings reveal that Nan Sakato values can function as culturally grounded interaction norms within cooperative learning. These values support deliberation, solidarity, responsibility, and adherence to shared expectations, thereby shaping students’ participation and mathematical discourse. The study contributes a transferable design principle for culturally responsive mathematics education by demonstrating that local cultural values can be operationalized not only as contextual resources but also as mechanisms for organizing disciplinary interaction.