Life Course Theory contends that school transitions can interrupt academic and wellbeing trajectories, depending on child, family, and school factors. Hierarchical regression analyses examined how autistic traits were associated with school transition outcomes. Autistic traits explained 12% of the variance in Quality of Life (QOL), 24% of the variance in mental health and 9% of the variance in school belonging. When autistic traits were accounted for, gender was a significant predictor of changes in QOL whereas changes in school belonging were predicted by cognitive functioning, parent education, school attendance and school refusal. Changes in mental health after transition were mostly predicted by family factors including family structure, family functioning and parent education but were also significantly predicted by sleep problems.