This paper presents data from a Forest School project aimed at impacting upon children and young people's emotional wellbeing. It uses a theory of change methodology to evaluate impact and explore the causal processes within the project. Mixed methods data are presented and analysed in relation to how different parts of the Forest School approach, as defined by the principles, lead to impact. The data demonstrate that whilst impact was seen for all, for individual young people the impact has been significant in specific ways. It would appear that many of the children and young people were able to develop in different ways to their peers and we argue 'take what they need' from their Forest School experience. Theory of change has been demonstrated to be a valid and useful tool in evidencing the complex processes that lead to change through a Forest School approach.