Mental health is not simply the absence of mental illness, but also the development of positive wellbeing. This notion has been reflected in recent theories around the ‘complete state’ model of mental health and reiterated by policy initiatives within schooling systems, who have placed a greater priority on supporting students’ wellbeing. Schools often act as a prevention and early intervention service for children and adolescents at risk of mental illness, operating with general and targeted wellbeing programs. Therefore, understanding the different types of trajectories of students’ wellbeing and identify critical transition periods when wellbeing begins to deteriorate will help inform schools prevention efforts. The current study utilises linked population-level census data collected from the South Australian Wellbeing and Engagement Collection to understand the trajectories of sadness, worries, happiness and life satisfaction. The sample included government students who completed the WEC in Grade 6 in 2016 and participated in one or more subsequent WEC surveys in 2017 (Grade 7), 2018 (Grade 8), or 2019 (Grade 9). The sample were split by gender in all analyses (females = 4182, males = 4197). Examination of longitudinal trajectories for each wellbeing variable was conducted through an iterative model testing process of growth curve analysis and varyingly-restricted mixture model estimation. Results indicated four distinct trajectory classes was the best fitting models for each of the wellbeing variables, except for life satisfaction where a three-class model was best fitting. Trajectory classes for all wellbeing variables, split by gender, will be presented. Concerningly, 19.7% of the female sample were classified in a ‘high stable’ sadness trajectory, 39.5% of females were classified as either ‘high or very high stable’ worries and 37.7% of males also had ‘high stable’ worries. Implications for how the identifications of different trajectories groups can inform universal and targeted school interventions will be discussed.