The purpose of this study was to examine the effects of parental support perceived by adolescents from low-income families on school adjustment, and to examine the indirect effects of learned helplessness on the relationship between parental support and school adjustment using longitudinal data. Specifically, this study examined the mediating effect of learned helplessness in the relationship between parental support in the first year perceived by adolescents from low-income families and school adjustment in the third year. For this purpose, this study used the data of 375 respondents who responded for three consecutive years from 2018 to 2020 in the longitudinal study of underprivileged children and adolescents surveyed by the Samsung Dream Scholarship Foundation, and conducted descriptive statistical analysis, correlation analysis, and structural model analysis. Bootstrapping was conducted to examine the significance of the indirect effect. According to the results of the study, parental support in the first year had a positive effect on school adjustment in the third year and a negative effect on learned helplessness in the second year. In addition, learned helplessness in the second year had a negative effect on school adjustment in the third year, and the indirect effect of learned helplessness in the second year was significant between parental support in the first year perceived by low-income adolescents and school adjustment in the third year.In other words, the higher the perceived parental support of low-income adolescents, the less learned helplessness and the more positive school adjustment.