Classroom walkthroughs are the consistent and systematic observation of instruction in the classroom, and despite research indicating classroom walkthroughs drive student achievement and promote learning, high school principals fail to implement effective classroom walkthroughs on a consistent basis, resulting in teachers not receiving enough guidance and support to improve instruction for student learners. The purpose of this study was to assist and empower high school principals as instructional leaders through the creation of a systematic classroom walkthrough process focused on providing instructional support to influence student learning outcomes in the classroom positively. The following questions provided the framework for the research: What values, opinions, or beliefs prevent high school principals from implementing effective classroom walkthroughs on a consistent basis? What is the structure of an effective classroom walkthrough that can be implemented successfully by high school principals? The study centered on action research, and I conducted data collection with an identified high school principal using a codesigned classroom walkthrough process. I also conducted a detailed qualitative interview to establish a basis of understanding for the values, opinions, and Through the codesigned action research framework McNiff (2017) outlined, the high school principal participant and the instructional leadership team followed a 12-step process to determine objectives, consider resources and timelines, articulate criteria, and conduct three weekly iterative rounds of classroom walkthroughs to collect data. The high school principal and the instructional leadership team monitored, analyzed, and interpreted the collected classroom walkthrough data to propose modifications and identify an action plan consisting of three major priorities to inform future action. The focus of the qualitative action research design was to support the revival of the instructional leader within public education by offering a well-developed theory for use of a redefined classroom walkthrough process to improve 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]