In this symposium we want to discuss agency as a critical perspective related to the main actors in schools namely students, teachers and school leaders. More specifically, we want to describe different examples of how agency may be identified, conceptualized and scrutinized in studies in classrooms and school settings. Agency as a concept relates to different traditions in psychological (Schlosser, 2019), sociological (Emirbayer & Mische, 1998) or post-humanistic practice-based theories (Priestley, Biesta, & Robinson, 2015). It is a concept also used to set policy directions such in OECDs (2019) conceptual learning framework for students. We want to deepen our knowledge about the agency concept through reflecting over how and in relation to what the critical dimension of agency comes into use in our research approaches and research fields of didactics, professional development and school leadership. Agency as the power of acting is important in different research projects that we work with. In the four studies presented here, the power of acting is closely related to knowledge and competence for the actors in focus (students, teachers, school leaders and/or researchers). The agency relates to two dimensions, 1) to be able to handle life and/or one’s own professional life (technical and practical knowledge and competence), 2) to be able to act for transforming learning, teaching and/or leading practices (critical knowledge and competence). The two dimensions does not exclude each other but could rather be seen as a continuum along which actors move dependent on situations and practical arrangements. This relation constitute agency but can be described, conceptualized and studied in different ways. The first study in this symposium critically analyses enabling and disabling factors for student participation in school improvement practices in the light of democratic views of education in the Nordic countries. In the next presentation the concept of agency is used to scrutinize how principals understand and manage controversial issues, an urging area for every school and school leader today. In the third study self-recognition is seen as an important aspect to strengthen teacher agency in knowledge production together with researchers in practice-based research. The last presentation is exploring how different teaching approaches are used in order for students to develop subject specific concepts for critically reviewing discourses in society where more elaborated second order thinking concepts is discussed in terms of emergent critical literacy and student agency.