Drawing on 3rd wave data from Korean Education Longitudinal Study(KELS)2013, we investigated the structural relationships between family background, social capital in the family and at school, and educational aspirations among junior high school students using the structural equation modeling(SEM). Our SEM results indicated that parental education and household income were robust predictors of students’ educational aspirations. In addition, the higher the level of parental education or household income, the stronger the parent-child relationships proved to be. It was also found that the parent-child relationships exerted a strong influence on teacher-student relationships and peer relationships as well as on educational aspirations. While family background had little to do with teacher-student relationships, peer relationships were not free from the influence of family background. Specifically, household income had a statistically significant effect on peer relationships, and parent-child relationships, which were strongly influenced by parental education and household income, had a strong effect on peer relationships. On the other hand, teacher-student relationships were closely associated with educational aspirations, but peer relationships had little to do with educational aspirations. Based on these findings, it is recommended that educators utilize teacher-student relationships, which are relatively free from the effect of parental education and household income, to close the gap in educational aspirations between the classes.