This study explored how teachers and school administrators connect large-scale assessment results with school improvement planning. Using a semi-structured format, 20 teachers and 18 administrators were interviewed from two school districts in southern Ontario, Canada. The interview protocol contained a range of questions related to teaching and administrative experience, large-scale assessment knowledge, professional development, and instructional planning in response to large-scale assessment results. Analysis of the interviews followed a constant comparison method and suggested few educators, particularly at the secondary level, were able to use large-scale assessment results in a sophisticated fashion for data-driven decision-making. The implications of the findings are discussed in relation to professional development, capacity building, and instructional leadership.