Background: The conceptual framework for "School as a Protective Factor" approach was presented in a companion article in this issue of the journal. The current article describes the validation of the "School as a Protective Factor-Brief (SPF-Brief)," a 13-item survey measuring the 3 core constructs and 13 defining characteristics of this framework. Methods: The "SPF-Brief" was validated through 2 studies. The developmental study used a longitudinal design including 1349 participants who completed surveys over 5 semesters, while the validation study used a cross-sectional design with 2775 participants. Both studies included middle and high school students. Factor analysis, growth model analysis, criterion-related validation, and outcome analysis were employed. Results: Analyses provided strong evidence supporting the reliability and validity of the instrument and conceptual framework. Higher "SPF-Brief" scores were associated with higher math grades, English grades, and quality of life, as well as lower rates of anxiety, depression, conduct disorder, alcohol, e-cigarette, tobacco, and cannabis use. Effect size estimates ranged from moderate to strong. Conclusions: These findings suggest the utility of the "SPF-Brief" instrument and the "School as a Protective Factor" framework. Together, they may offer advantages to the traditional school climate approach.