The vast majority of studies that have examined the classroom teacher's impact on student learning have come to a simple conclusion: Out of all aspects of schooling, the teacher has
the most positive impact on student learning (for a review of several studies, see Nye, Konstantopoulos, & Hedges, 2004).
If test results show significant widespread gains in
student results temporally associated with district reform plans, if these trends are generalized across all or
most schools, and if the performance gaps between previous groups of low and high performing
students and schools are seen to be diminishing over time, the argument is made that district reform efforts are having a
positive impact on student learning.