Abstract
Leadership training primarily targets individuals, yet distributed leadership theory views leadership as shared across actors. This study tests whether leadership training effects display distributed properties when multiple leadership team members are trained over time, distinguishing between additive effects (cumulative organizational gains as more members train) and concertive effects (multiplicative gains via collaboration). Using longitudinal data from 2009 to 2021, we analyze 18,563 person-year observations from 3,783 principals and assistant principals using dynamic difference-in-differences and multilevel approaches. Outcomes are student achievement measures and teacher ratings of instructional leadership. Results show that sequencing matters: when principals are trained first, concertive mechanisms boost student achievement. Yet teacher ratings of instructional leadership decline when principals are trained first, suggesting a redistribution of leadership across teams. Findings challenge individual-focused training evaluations and support the potential of distributed mechanisms of leadership training, highlighting the importance of strategic training order in leadership teams.