Children in the UK have poor health compared to other Western European countries, and there are large and increasing inequalities in child health, including for mental health and obesity. Over the last 20 years numerous reviews of evidence and policy have repeatedly emphasised the need to provide better support early in children’s lives if we are to have any chance of significantly reducing the inequalities in life chances experienced by people in the UK. To address these challenges, we propose a programme of work with a focus on harnessing data to evaluate systems-based approaches for improving children and young people’s outcomes.