The objective of this article is to discuss actions of agency by analyzing the practices and conceptions of a mathematics teacher working in the municipal school system of Valinhos, state of São Paulo, while teaching statistics and probability to students in the final years of elementary school. The concept of agency is related to transformative capacity and refers to the power of the individual over the context in which they are inserted. The concept of agency is significant for teacher

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... on and is linked to critical professional development, as criticality is essential for people's transformation processes. This study adopted principles of (auto) biographical research, which view narratives as training and self-training practices. Through spoken and written narratives given by a teacher who participated in a collaborative study group, discussions about the way she develops her practices and the factors that most influence her decision-making are examined.