Adolescent health researchers and practitioners are frequently interested in assessing depression as part of student screening and for school-wide prevention and intervention planning. However, this task is challenging given the lack of free, brief assessments of depressive symptoms in youth. This study evaluated the psychometric properties of an adapted version of the Modified Depression Scale (MDS). Data came from a school-based survey of 9th-12th graders in Boston (N=1,657). We assessed internal consistency reliability and known-groups validity, in addition to the feasibility of establishing a dichotomous cut-point to classify adolescents as having high versus low depressive symptoms. We also evaluated the validity of the adapted MDS as a school-wide measure. At the student-level, the adapted MDS demonstrated acceptable internal consistency. Students engaging in risk behaviors (e.g., substance use) or who were victimized (e.g., bullied) had significantly higher depressive symptom scores. Students who endorsed four or five MDS symptoms often or always had a heightened risk of suicidal ideation, substance use, and failing grades when compared to students who endorsed three or fewer symptoms often or always. At the school-level, higher mean levels of depressive symptoms in a school were associated with higher mean levels of suicidal ideation and failing grades. Results of this study suggest that the adapted MDS is a promising measurement tool that could be useful to school-based professionals and researchers to evaluate depressive symptoms in adolescents and ascertain the prevalence of depressive symptoms in schools.