This is a psychometric analysis of an instrument to assess the socio-emotional development of school students, How I Feel (HIF), developed as a situational judgment test, with scoring based on expert judgments. The HIF test was administered in grades 4-9, 1999-2005. Internal consistency, retest reliability, and year-to-year stability were satisfactory, and the HIF instrument appears sensitive to intervention effects. Sex differences and associations with substance use and other instruments support construct validity. A significant negative trend was found across grades, attenuated in a group receiving socio-emotional training. The HIF test has limited discriminatory power among individuals with high socio-emotional maturity. (Contains 1 table and 2 figures.)