Assisting in the Preparation Process for Students Competing in the Mathematics Olympiad at X School

This study aims to evaluate the application of the Mastery Learning model in mentoring for the National Science Olympiad (OSN) using a class action research model. The research subjects consisted of students from grades XI and XII, with each class represented by 10 students, resulting in a total of 20 students. The OSN mentoring process was structured in a cyclical format, consisting of the stages of planning, action, observation, and reflection. The methods employed in this study included observation, testing, and documentation, which provided a comprehensive understanding of the learning process and its impact. The results of the study showed that the application of the Mastery Learning model significantly influenced the improvement of students' mathematics learning outcomes. Initially, before the first cycle, the students' understanding was recorded at 65%. However, after the first cycle, their understanding improved to 75%. Following the second cycle, the students' understanding further increased to 90%. In addition to this, the average score of learning outcomes showed a notable improvement, from 71 in the first cycle to 87 in the second cycle, reflecting the success of the Mastery Learning model in enhancing student comprehension. This study demonstrates that the Mastery Learning model, when applied in the context of OSN mentoring, can significantly improve students' mathematics learning outcomes, which in turn positively influences their preparation for the national OSN competition. This improvement is an indication of the effectiveness of Mastery Learning in fostering a deeper and more comprehensive understanding of the subject matter. As a result, this model has the potential to be applied in various educational contexts to enhance student learning outcomes, contribute to academic success, and support achievement in competitive academic settings.