This quantitative survey-design research study examined elementary school principals' perceptions regarding the effect of No Child Left Behind (NCLB). A primary focus of the study was to determine how elementary school principals feel about the influence of NCLB on their role as instructional leader. A sample of 133 elementary school principals provided data for the study, where seventy-four (74) were in schools that met adequate yearly progress (AYP) goals and fifty-nine (59) in schools that did not meet AYP goals. Pearson correlations and multivariate analysis of variance procedures were used to determine the strength and direction of relationships among the variables and differences in subscales assessing perceptions of NCLB effects on instructional leadership, leadership strategies, school morale and vision, and administrative tasks. MANOVA results revealed no significant multivariate differences on the 4 subscales of perceived NCLB effects across AYP performance. However, segmented correlation analyses within AYP groups revealed that perceptions of NCLB effects on administrative tasks was positively related to perceptions that NCLB affects instruction leadership role and strategies of effective leadership regardless of AYP status. The emphasis on high stakes testing requirements implemented by NCLB has affected all students regardless of socioeconomic status along with its affect on the leadership practice of elementary school principals. This research will add to positive social change by informing training and professional development programs which can help new elementary school principals become effective instructional leaders while also furthering NCLB accountability efforts to increase student achievement. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]