Objectives: This study aims to examine a school adjustment trajectory of adolescents from continued single parent families and its associated factors by comparing it to that of adolescents of two-parent families. Methods: We selected 4th grade students from Korean Youth & Youth Panel Survey (KCYPS). Using a multi-level growth modeling, we followed the trajectory of school adjustment until 9th grade and the effects of family income, parenting styles, and academic motivations of adolescents on the intercepts and the slopes. Results: Adolescents' school adjustment were decreased from 4th grade to 7th grade and then increased from 7th to 9th grade. The adolescents of continued single parent families showed a lower school adjustment than those of two parent families and this trend remained constant during the period. The effects of family income, parenting style, and academic motivation were confirmed to explain the gap between the adolescents of single parent and two parent families. Conclusions: The results imply that an earlier intervention is necessary to reduce the gap. We need to offer income support and decent quality of work for single parent family to reduce the economic hardship and also provide parental education that is designed to enhance academic expectations and motivations.