In this study, using the 4th (2019) and 5th (2020) data of the 1st grade panel in the middle school of the Busan Longitudinal Study of Education, we looked at how high school students' parents-children communication affects their academic achievement through mental health and self-directed learning, focusing on pre- and post-COVID 19. For this purpose, the results of analysis using the paired sample t-test and structural equation model are as follows. First, after COVID 19, achievement in mental health and mathematics declined, while self-directed learning, Korean, and English achievement increased. Second, parents-children communication had a positively significant effect on mental health and self-directed learning. In addition, it was found that mental health had a positive effect on self-directed learning, and self-directed learning had a positive effect on academic achievement. Third, parents-children communication showed an indirect effect on academic achievement through self-directed learning and mental health showed an indirect effect on academic achievement through self-directed learning. The implications are as follows. Since communication between parents and their children affects the emotions and cognition of their children, it is necessary to recognize the importance of the role of parents in the family and to provide parental education for smooth communication within the home.