Altered family experiences place children in foster care at risk for school adjustment difficulties. This study focuses on exploring the differences in school adaptation, locus of control, depression symptoms, and attachment styles among children in foster care and children raised by their biological parents. Sixty children completed self-report questionnaires; 30 of them were in foster care (mean age of 12.11 years), and 30 of them were in biological families (mean age of 12.9 years). Significant differences between the two groups were found regarding attachment. Those in the foster care group were more often characterized by an avoidant attachment style than those in the biological families group. Avoidant attachment style was found to be associated with locus of control over school failure, dysphoria, and social problems in children in foster care, but not for children in biological families. Based on our findings, school-based interventions for foster children should focus on basic emotional needs regarding their vulnerable self-perception, defense mechanisms, and difficulties in developing secure relationships with others (i.e., classmates and teachers).