Given that youth mental health is associated with success in school and life more broadly, it is important that school-based psychological service providers embrace best-practice prevention and intervention strategies that target mental health when working with student populations. One line of study in this area has begun exploring the incorporation of a dual-factor model of mental health within universal screening systems in schools. The dual-factor model is differentiated from the traditional unidimensional mental health model, which focuses on the presence or absence of psychopathology, by conceptualizing mental health alternatively as consisting of both psychopathology and wellbeing dimensions. The present study involved the preliminary development and validation of the Student Wellbeing Teacher-Report Scale (SWTRS)--a brief behavior rating scale intended as a screening tool for measuring the wellbeing dimension of youths' mental health at school. Specifically, the study involved drafting pilot items for the SWTRS and explored their latent factor structure, concurrent validity with school-related outcomes (i.e., attendance, academic achievement, and time on-task), as well as concurrent and incremental validity in comparison with two psychopathology screeners. Results suggested that the SWTRS items may better represent three context-specific indicators of youth wellbeing behavior--(a) academic, (b) social, and (c) emotional wellbeing--rather than the hypothesized "feeling good" and "functioning well" dimensions. The SWTRS scores also demonstrated incremental validity and were uniformly stronger concurrent predictors of all school-related outcomes compared to the psychopathology scales. Implications for theory and future research are discussed.