In this chapter, we aim to advance our understanding of how education can harness students’ capabilities to collectively deal with and act on major challenges, such as the ecological crisis. We examine students’ agency formation in an environmental action project in a rural high school in Southern Finland. In the project, the students interacted with young climate activists, local politicians, and other local stakeholders to envision and contribute to changes in ways of living and organizing activity in the school and beyond. In using the term “agency,” we refer to the students’ opportunity, will, and skill to act upon, influence, and transform activities and circumstances in their lives and communities. The chapter draws on the concepts of demands and motives, foregrounding the dialectic between individuals’ opportunities and demands related to the practices they inhabit. Drawing on longitudinal student interviews, this study asks the following questions: What are the motive orientations that diverse youth attach to the environmental actions project, and how do these interact over time with the various emergent demands of the activity and opportunities for action in and outside of school? How does the students’ agency develop over time through their engagement with the project?