In 2019 the Department for Education (DfE) published Relationships, Sex and Health Education (RSHE) statutory guidance, which outlines what schools should teach their pupils about relationships, sex, health and wellbeing. Schools had one year to prepare for implementation before first teaching in September 2020, although because of the pressures on schools during the pandemic, DfE allowed for some flexibility. This report presents findings from research conducted by IFF Research on behalf of DfE, which explored how the guidance has been implemented in schools, as well as how closely the implementation of the guidance has lined up with the Department's Theory of Change. The key findings of the research suggest that overall, the theory of change, including the activities, outputs, outcomes, and underlying assumptions, partially align with the actual practices in the schools. Schools have engaged with and implemented the new curriculum using a range of different approaches, adapting the guidance flexibly to the context of their school. Further research may be required to gain a better understanding of how effective the different approaches used by schools were, the barriers that schools were still facing, and possible solutions to address them.