The validity of the Single-Item Self-Esteem Scale (SISE) in adolescents was not well established, and how self-esteem manifested in newly incarcerated juvenile delinquents was poorly described. Using a retrospective study with archival records, the SISE was compared to other measures of self-esteem, grit, mental health, and academic self-concept in a small juvenile detention center in the Midwest of the United States. Demographic data were analyzed, and a correlation, intraclass correlation, and kappa statistic were run to test relationships and reliability. The SISE was found to be a reliable and efficient tool to use with adolescents and juvenile delinquents. Policy recommendations applicable to juvenile delinquents and schools in general give direction using the findings.