Parents play a major role in children's development and have unique opportunities to observe a wide range of their children's social-emotional behavior at home and in their communities. Yet parents' input via universal screening assessments into school-based social-emotional learning (SEL) programs for their children has been limited by a paucity of efficient, valid assessments of CASEL-aligned SEL competencies and potentially co-occurring emotional behavior concerns. This article describes the use of item response theory methods to develop brief emotional behavior concerns (EBC) scales designed to expand the Parent version of the CASEL-aligned SSIS SEL Brief Scales (SSIS SEL"b") that enables a sound assessment of the whole social-emotional child. Specifically, the article examines the initial psychometrics and utility of EBC-Externalizing and EBC-Internalizing scales for parents. The results showed the assessment of SEL skills and EBC behaviors to maximize efficiency and yield scores that provide valid insights regarding the interplay of these behavior constructs. The Parent version of the SSIS SEL Brief + Mental Health Scales expands assessment options for practitioners to allow efficient incorporation of parent perspectives about the whole social-emotional child. The article concludes with a discussion of limitations and future research.