The purpose of this study is to identify the factors that affect middle school students’ Korean language achievement and the relationship between them. In order to achieve the purpose of this study, the three-year data of the Busan Education Longitudinal Study were analyzed by applying the change process of teaching-learning activities and the latent growth modeling. As a result of the study, it was confirmed that the Korean language academic achievement of middle school students in Busan is continuously increasing. In addition, the awareness for teachers was declining, and the correlation between teaching-learning activity factors and Korean language academic achievement was low, but the correlation between teacher-related factors was high. It was reported that the correlation of affective factors was higher than that of cognitive factors. As a result of analyzing by applying the latent growth modeling, it was found that reading activity, efficacy, interest, and attitude in the 1st year had a significant effect on the initial value of the multiple-choice score in Korean. As the influence on the change value showed a negative relationship, it was confirmed that the duration of the influence of the affective factor was not long. Policy recommendations based on the research results are as follows. Provision of educational interventions that can stimulate learners’ affective factors, expansion of teacher re-education opportunities to raise learners’ awareness for teachers and immersion in reading to increase the influence of reading activities It is necessary to create the conditions for writing, develop a writing program, and conduct qualitative research in parallel with quantitative research.