The purpose of this study was to examine the number of latent groups and the outcomes of latent group-specific predictor variables and outcome variables according to the development of grit during adolescence (from 8th grade to 12th grade), and to derive implications for the school curriculum. The study analyzed data from 1,624 participants (51.7% male, 48.3% female) over a period of four years from the second (2018) to the third (2021) wave of the Daegu Education Longitudinal Study. The results of the study are as follows: Firstly, grit showed a quadratic developmental trajectory, and latent groups were classified into two based on changes in grit: “high-level maintenance-increasing type” and “low-level maintenance-decreasing type”. Secondly, in terms of the predictability of learner characteristics by latent group based on changes in grit, self-esteem, career maturity, morality, creativity, and sociability were all more likely to belong to the “high-level maintenance-increasing type” group than the “low-level maintenance-decreasing type” group. Based on the research findings, implications for educational curriculum to enhance grit during adolescence were discussed.