 This study examined the mental health trajectories of children and adolescents during the COVID-19 pandemic. It found that most young people experienced low-stable symptoms, however, nearly one-third experienced high-stable or increasing mental health difficulties. Those with complex needs and parents with higher psychological distress were particularly vulnerable to high-stable problems while those with positive peer relationships were less vulnerable. This study provides insight into potential factors that can be addressed through targeted interventions to improve the well-being of parents and young people in the event of future lockdowns and school closures. This article was authored by Carolina Guzman Holst, Lucy Boats, Polly Wait and others.