The purpose of this study was to determine the extent secondary assistant principals in large Texas high schools demonstrate behaviors consistent with what the literature describes as instructional leadership. Three hundred seventy principals and assistant principals of large Texas high schools participated in this study. The Principal Instructional Management Rating Scale (Hallinger, 1987) was used to quantify instructional leadership in 10 different job functions. The study found that (a) assistant principals perceive themselves as exhibiting instructional leadership behaviors at a high frequency, (b) principals perceive their assistant principals exhibiting instructional leadership behaviors at a high frequency, (c) the perceptions of the principals and assistant principals were similar, and (d) principals and assistant principals reported more engagement in instructional leadership responsibilities and felt more pressured over the last five years under the new accountability and rating requirements of No Child Left Behind and the state assessments. These findings suggested that the administrative roles and responsibilities in high schools should be restructured to allow assistant principals to focus on instructional leadership. [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.]