<![CDATA[The low mathematics learning outcomes of third-grade students at SD Swasta Kenanga Medan were caused by the limited use of teaching methods and learning media, resulting in monotonous learning activities, decreased learning motivation, and a lack of student participation and concentration during the learning process. This Classroom Action Research (CAR) aimed to improve students’ mathematics learning outcomes through the implementation of the Student Teams Achievement Division (STAD) cooperative learning model. The study was conducted on 20 third-grade students of SD Swasta Kenanga Medan in the 2025/2026 academic year. The research was carried out in two cycles, each consisting of planning, action, observation, and reflection stages. Data were collected through tests, observations, and documentation. Initial observations showed that students’ mathematics learning outcomes were still low, with a classical learning mastery level of only 30%, or 6 students achieving the Minimum Mastery Criterion (MMC). The STAD learning model was implemented through the formation of heterogeneous groups, group discussions, individual quizzes, and group rewards. Through this model, students were encouraged to participate actively, collaborate with their peers, exchange ideas, and take responsibility for both individual and group learning tasks. The results of the study indicated that the implementation of the STAD cooperative learning model was able to improve students’ mathematics learning outcomes. At the end of Cycle II, the classical learning mastery reached 75% and met the predetermined success indicators. Therefore, the STAD cooperative learning model was effective in improving the mathematics learning outcomes of third-grade students at SD Swasta Kenanga Medan.]]>
