Although the importance of school leadership in student learning and staff retention has been well-documented by research, minimal research exists on the practices of effective Christian school leaders and how those contribute to school sustainability and fulfillment of mission. Steward leadership theory has been researched and applied to other nonprofit areas, yet it is unknown how steward leadership practices impact the success of K-12 Christian school superintendents and the sustainability of Christian schools. Using a qualitative, phenomenological analysis of interview data derived from 15 school superintendents, this current research sought to analyze the lived experiences of K-12 Christian school superintendents to understand how the leadership beliefs, sustainability practices, and mission-fulfillment practices of these superintendents aligned with steward leadership theory. Three emergent, overarching themes were identified following the coding and categorization of the data: required relationship, courageous humility, and the quest for missional alignment. The findings of this study support a connection between steward leadership practices and beliefs and Christian schools that are sustainable and mission achieving. Drawing a connection between steward leadership theory and successful practices in Christian schools may allow for distinctive training to be developed to further strengthen these unique organizations. [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.]