The biggest challenge facing American public schools today is increasing student achievement, and this depends on the educational system's ability to improve the quality of instruction. Principals play a key role in improving the quality of instruction on their campus through the instructional leadership practices they engage in on a daily basis. If the quality of instruction across the nation is going to increase, principals will be one of the key factors to making this a reality. Evaluation systems for principals serve two purposes. They rate or measure effectiveness, but perhaps more importantly they provide feedback and support in order to improve practice. In light of a new nationwide focus on accountability, school districts across the United States are revamping their vague and outdated principal evaluation systems in order to incorporate more accurate tools aligned to current empirical research in the field of principal effectiveness. The Vanderbilt Assessment of Leadership in Education (VAL-ED) is one tool that has been recently developed and holds potential to help with transforming existing nondescript principal evaluations into evidence-based meaningful interactions. The researcher used quantitative methods to analyze teacher, principal, and supervisor ratings of principal practices on the VAL-ED assessment to examine the consistency of ratings among types of respondents and the difference between effective and ineffective principals in regard to the core components and key processes included within effective principal practices. Findings revealed that respondents do not always share the same perspective of the effectiveness of the principal, and the results provide data helpful to principals aimed at improving their own practice. This study could serve as a model for using input from the VAL-ED assessment of principals to more precisely focus efforts and resources to improve instructional leadership of principals. [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.]