Based on evidence from a large-scale leadership waning field experiment, this arricle advances our knowledge about the possibilities for training leaders toward more active and effective leadership. In the field experiment, public and private leaders were randomly asrigned to a control group or ame of chree leadership training programs: Transformational, transactional, or a combined program. Employee responses from 463 organizations show that the training can affect leadership behavior positively in very different orgunizarions (primary and secondary school, daycare centers, tax centers, and bank units). Furthermore, far the subsample of school principals, we find some evidence of training effects on performance in standardized tests in elementary schools and final exams in lower secondary schools, We discuss these findings in relation to training content am performance criteria.