This research study addressed measuring the level of instructional leadership effectiveness of the high school assistant principal and the high school instructional leadership teams (ILT) at over forty (40) Shelby County Schools. More specifically, this research study examined their impact on teacher effectiveness and student achievement in their respective high schools. Two Spearman RO tests were used to determine whether significant relationships existed (a) among the high school assistant principals, his/her instructional leadership teams (ILTs)'s INSIGHT survey ratings and their high school English II EOC teachers' TVAAS growth data and (b) high school assistant principals, his/her instructional leadership teams (ILTs)'s INSIGHT survey ratings and their high school students' English II EOC achievement data. The results revealed that there was no significant relationship among leader-teacher scores and leader-student scores among all three data sets: INSIGHT school leader survey results, TVAAS teacher growth data and English II EOC student achievement data. Consequently, high school teachers who were led by assistant principals and their high school instructional leadership teams that helped them to enhance their learning environments and provided high quality professional development did experience an increase in their TVAAS teacher growth data. In addition, high school students who were led by assistant principals and their high school instructional leadership teams that focused on planning high quality lesson plans/assessments and provided a rigorous, competitive academic cultural environment did experience an increase in their English II EOC student data. This research study is increasingly important as we embark upon College and Career Readiness Standards (CCRS) teaching and TN Ready/Common Core testing in the next era of public school education. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]