Purpose: This study examines how principals’ exercise of individual autonomy and discretion shapes their roles as street-level managers, bridging the gap between strategic goals and operational demands in precarious institutional contexts. The paper contributes to an emerging area of research and offers valuable empirical evidence. Research Methods: A longitudinal qualitative design involved semi-structured interviews with 14 purposively sampled school principals over three years. Grounded theory principles guided data analysis, employing synchronic and diachronic approaches with open and axial coding. Triangulation and comparative category analysis were conducted iteratively. Findings: The analysis traces the evolution of principals’ strategies during the implementation of the Chilean New Public Education Law. In response to perceived abandonment by the middle tier, unclear guidelines, and community demands, principals exercised autonomy through three adaptive strategies: Collective Influence to strengthen systemic impact; Territorial Networks to secure essential resources; and Pedagogical Improvement to sustain educational quality despite challenges. These practices illustrate how principals adapted to the improvised reform and transformed institutional contexts. Implications for Research and Practice: This study contributes to the understanding of principals as street-level managers by documenting how their use of individual autonomy evolves to adapt and respond to educational reforms and institutional changes. It highlights the need for longitudinal research to capture how principals’ adaptive strategies influence policy design and implementation.