Objectives: The purpose of the study was to not only classify the latent class according to the trajectory of changes in the school adjustment of elementary school children in Grades 1-3, but also analyze the factors affecting school adjustment. Methods: Data from the Panel Study on Korean Children of the Korea Institute of Childcare and Education were analyzed from wave 7 (2014) to wave 10 (2017). The growth mixture model was applied to derive the latent class according to the trajectory of changes in the elementary school adjustment of children in Grades 1-3. A multiple logistic regression analysis was conducted to analyze whether school readiness, social competence, play interaction, play interference, and play interruption affected the latent class classification of school adjustment. Results: First, the growth trajectory of the sub-factors of school adjustment revealed the latent groups of 2 to 3. Second, the potential groups of school adjustment of elementary students in Grades 1-3 were identified as follows: (1) adaptation-decreasing, (2) high adaptation-stable, (3) adaptation-increasing, and (4) low adaptation-stable. Third, the factors that had significant effects on the latent class types of school adjustment were school readiness, social competence, and play interference. Conclusion: The results of the study revealed the growth trajectories of elementary school children's school adjustment, suggesting the importance of improving school readiness, social competence, and play competence, which affect school adjustment trajectories.