This report describes the findings of an analysis of a series of action research projects conducted by Vigo County School Corporation at Terre Haute North Vigo High School (hereinafter referred to as North Vigo). During the 2008-2009 school year, 19 teachers at North Vigo participated in independent action research studies regarding the extent to which selected instructional strategies enhanced the learning of students. Participating teachers selected two groups of students both of which were being taught the same unit or set of related lessons. However, in one group (the "treatment" group) a specific instructional strategy was used, whereas in the other group (the "control" group) the strategy was not used. The average effect size for all 19 independent action research studies was statistically significant (p less than 0.01). A reasonable inference is that the overall effect of a 13 percentile point gain is probably not a function of random factors that are specific to the independent action research studies; rather, the 13 percentile point increase represents a real change in student learning. Instructions for Action Research are appended. (Contains 7 figures and 3 technical notes.)