Assistant principals as content-focused instructional leaders are an essential component of educational reform. Continued state and federal accountability for improved student learning requires promoting assistant principals beyond managerial duties toward increased supervision as instructional leaders. Unfortunately, administrators at the high school level frequently lack content knowledge in the areas they supervise. A critical analysis of the position was needed knowing assistant principals are influential in the teaching and learning process. The first research question determined how and in what ways assistant principals who supervised instruction at the high school level made sense of their position dependent upon whether they were highly qualified in the content areas they supervised. The second research question acknowledged the lived experiences of participants and gained insight of their perspectives related to the relationship between their content area base of expertise and their self-efficacy around supervising both familiar and unfamiliar content areas. The study included a theoretical framework of instructional leadership with an emphasis on content as well as a conceptual framework of self-efficacy. The methods used to complete the study incorporated a grounded theory qualitative approach to include purposive and snowball sampling techniques. Participant recruitment was based on specified criteria of high school assistant principals who supervised instruction. Each participant engaged in an interview with the researcher where data collected from all contributors were thoroughly analyzed by using open coding, axial coding, and selective coding. The overall findings interconnected with the literature revealed three major categories of consideration. The first category was the ability of the assistant principal to balance the roles and responsibilities associated with the position. The second category addressed the influence of having a highly qualified status in relation to being a content-focused instructional leader. The final category included self-efficacy of the assistant principal as a content-focused instructional leader. The conclusion highlights the necessity to impart supports to enhance an assistant principal's ability to become a competent content-focused instructional leader. Furthermore, future research of assistant principals as content-focused instructional leaders is necessary as it has the potential to positively influence teacher professional growth and overall student learning. [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.]