In today's world, effective management is one of the main indices of development. Effective and capable managers, using their organization's potentials can provide a desirable context for permanent development. In this study the relationship between managers' effectiveness and the three factors of position's power, task structure, and leader-member relations has been examined in Najaf Abad high schools and art schools. In this descriptive study, the research population included 870 teachers and 60 administrators of whom a sample of 180 teachers and 20 administrators was randomly selected. The three instruments used were the leader questionnaire, the LPC questionnaire, and the managers' effectiveness questionnaire. The reliability of the instruments is 0.89, 0.96, and 0.97 respectively. The results show a positive correlation between managers effectiveness and: position power (r = 0.72), task structure (r = 0.71), and leader-member relations (r = 0.8). Leader-member relations and task structure together accounted for 0.77 of the variation in managers' effectiveness. The correlation between LPC scores and managers effectiveness was observed to be significant (r = 0.646, P£0.01).