This paper explores the arbitrariness in theory building and argue that the golden principle of parsimoniousness in scientific research has its cost. Based on the data of a study examining the dynamic impacts of school principals on changes in student learning through school improvements, a series of structural educational models are set up based on a set of variables related to principal values, principal efficacy, policy enactment, and leadership practices addressing rival theories such as transformational leadership and instructional leadership.

Evidence for the study was provided by 168 senior teachers of 41 schools to a survey, along with value-added student achievement data between 2006 and 2008. Path analytic techniques were adopted to address the objectives for the study.

Results indicated that parsimoniousness should not be the only criterion for evaluating rival models. Models set up to test the relative significance of constructs showed the shortcomings of leadership theories that failed to address policy enactment. Constructs under-researched like values and qualities of principals were found to be an important antecedent of principal efficacy. School leaders’ efficacy also had strong, positive impacts on the enactment of education reforms and school improvements.