Military-connected students (MCSs) face academic challenges because of frequent transitions. During military parents' permanent change in duty station (PCS), MCSs are absent for 15 days or more. PCS-related absenteeism has increased over the last decade, and academic achievement has decreased. This basic qualitative capstone project study examined the challenges of high school administrators from Southeast Asian Pacific Island district schools to provide teachers with systematic professional development that supports sustainable instruction for MCSs during PCS-related absences. The conceptual framework for the study was Hersey and Blanchard's situational leadership theory (SLT). SLT suggests that administrators adopt leadership approaches to combat PCS-related absenteeism based on the dynamics of their learning and working environments. This qualitative study used open-ended, semi-structured interviews to examine the perspectives of 10 high school administrators on PCS-related absenteeism and the challenges of providing teachers with systematic professional development (PD) that supports sustainable instruction for MCSs and SLT as a resource to meet teachers' PD needs. The study involved thematic analysis to identify seven themes (culture and climate, community, flexibility, mentorship, teacher readiness--PD, relationships, and social-emotional balance) that factor into improvement priorities. The findings of this capstone project study were used for positive social change by suggesting educational resources and PD strategies to the Department of Defense Education Activity's Pacific Center for Instructional Leadership team through a leadership approach that influences sustainable instruction for highly mobile MCSs during the transition. [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.]