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Many researchers have examined the impact of Headmasters´ managerial or leadership styles on school improvement. They have found either positive, negative or no impact of Headmasters´ roles on school improvement. Very few researchers have inquired to what extent a school changes if principals´ roles and teachers´ professional development work together with same spirit. Therefore, this researcher has tried to find whether the relationship between principals´ roles and school improvement become strong, weak or neutral with the presence of third variable teachers´ professional development. This research has given an insight what professional development activities a principal/headmaster should follow to strengthen the impact of his managerial roles on school improvement.

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