The Social Emotional Health Survey-Secondary-2020 (SEHS-S-2020) is a well-studied option for assessing social emotional health to support students within a multitiered system of school support. While a growing body of literature supports the SEHS-S-2020 measure for assessing student covitality, there is less validation evidence specifically for middle-school-aged students. The present study aimed to fill this gap in the literature by examining its use for younger adolescents. Study participants were from two samples, including a cross-sectional sample with 9,426 students in Grades 7-8 from 32 counties in California and a longitudinal sample with 414 students in Grades 6-8 from two middle schools. Data analyses examined structural validity, internal consistency, measurement invariance, criterion validity, predictive validity, and response stability. Results indicate excellent fit indices for a four-level higher-order measurement model, with adequate concurrent and one-year predictive validity coefficients, supporting the use of the SEHS-S-2020 measure with young adolescents in middle school settings. The discussion focuses on implications for assessing students' psychosocial assets, universal school-based screening, and cultural and intersectionality considerations when interpreting SEHS-S-2020 responses.