Dual-factor models of mental health are increasingly supported but little is known about longitudinal trends in dual-factor mental health. The current study used latent profile analysis (LPA) to empirically identify dual-factor mental health classes at each of Grades 9 through 12 and latent transition analysis (LTA) to examine stability of classes over four academic years. A sample of 875 adolescents from two cohorts reported on their social-emotional strengths and psychological distress. Cross-sectional LPAs for each grade year resulted in four mental health classes: "complete mental health," "moderately mentally healthy," "symptomatic but content," and "troubled." An LTA model indicated that the "complete mental health" class exhibited the most stability, followed by "moderately mentally healthy" and "symptomatic but content" classes. The "troubled" class exhibited the least stability. Less than 24% of participants remained in the same mental health class across all years. Findings support regular monitoring of students' dual-factor mental health to accurately inform mental health promotion, prevention, and intervention efforts. [This paper was published in "Journal of School Psychology" 2019.]