Is more always better? Rethinking the relationship between teacher leadership and student achievement

Over the past two decades, teacher leadership has become one of the prominent ideas among educational researchers, policy makers and practitioners as a promising direction for securing and sustaining school improvement. Based on data from the 2022 Program for International Student Assessment (PISA), we examine the question of whether ‘more is always better’ by studying the relationship between teacher leadership and student achievement. We found that there was an inverted U-shaped relationship between teacher leadership and student achievement, and identified a turning point beyond which higher teacher leadership is associated with lower student achievement. The findings challenge the current dominant approach and finding with only linear perspective on the relationship between teacher leadership and school outcomes. This finding moves the field beyond the assumption of ‘more is better’ and towards a more nuanced understanding that the effect of teacher leadership depends on the level, coordination, integration, and organisational arrangement for teacher leadership.