The purpose of this study was to explore the nature of the subgroups involved in, as well as the changes in the experience of career education by adolescents within school, focusing on the guidance experience from the Career Guidance and counseling Teacher (CGCT), and to compare the tendencies in career maturity development.  The longitudinal data sets from the Seoul Education Longitudinal Survey (SELS) conducted by the Seoul Metropolitan Office of Education, which contained the panel data from middle-school and high-school students from 2012 to 2015, Latent Class Growth Analysis (LCGA) and Growth Mixture Modeling (GMM) with known classes were utilized for this study. The results of the analysis were as follows: First, three latent classes were identified within the changes of career education experience from the CGCTs: a “consistently little experience group”, an “increasing experience group”, and a“decreasing experience group”. Second, there were statistically significant differences among the three latent trajectories in terms of adolescents’ self-respect, plans after graduation and school sector of high school. Third, the “increasing experience group” was shown to have the highest initial average but the lowest linear change rate of career maturity. On the other hand, the “decreasing experience group” was found to have the lowest initial average but the highest linear change rate. Based on these findings, we were able to discuss and explore the educational implications for career education and guidance in school.