This mixed methods descriptive and causal-comparative study investigates what instructional leadership behaviors effective California high school principals have and what their beliefs are in regards to pedagogy, related issues, and professional issues, either constructivist or instructivist in nature, in the environment of the current NCLB accountability era. Differences found in eight specific demographic variables were analyzed in combination with data obtained from principals' responses on the Principal Instructional Management Rating Scale (PIMRS) and the Principal Beliefs Survey (PBS, a variation of the Teacher Beliefs Survey). The population comprised of principals whose schools have met their API growth targets for two consecutive school years school wide and for socioeconomically disadvantaged, English learner subgroups. A volunteer rate of 51% (N = 36) was obtained from a population of 71. Results indicate that effective high school principals frequently engaged in instructional leadership behaviors. Concerning pedagogy, principals held eclectic beliefs, but were united in the beliefs of accountability and the importance of a prescriptive, well designed curriculum. Subjects' gender, ethnicity, and the percentage of instructional leadership delegated were not significantly different in regards to principals' instructional leadership practices or pedagogical beliefs. Significant differences were found among a few specific instructional leadership practices and pedagogical beliefs based on subjects' education level, overall years as a classroom teacher, subject taught as a teacher, overall years as the current principal, and overall years of administrative experience. From the findings, a contingency model of principals' pedagogical beliefs was developed. Additionally, reliability testing was performed on both instruments. [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.]