When Mission Stops Governing offers a rigorous examination of mission drift in merged schools and other mission-driven educational institutions. Rather than treating drift as a matter of declining sincerity or weakened identity language, the author argues that it emerges through structural reordering: shifts in authority, governance, budgeting, scheduling, hiring, evaluation, and institutional credibility that gradually allow managerial logic to overtake formative purpose Drawing on case-informed institutional analysis, the book develops a conceptual framework for understanding how mission moves from governing principle to symbolic theme. It traces the rise of hybrid institutional logics, the bureaucratic turn, operational drift, hidden labor, burnout, succession crises, and the widening gap between the school as formally described and the school as actually inhabited In response, the book offers more than critique. It proposes a disciplined account of reconstruction, showing how mission can be re-embedded in governance, decision pathways, leadership formation, and organizational design. Engaging questions of authority, legitimacy, symbolic life, and institutional memory, When Mission Stops Governing speaks to scholars of education, Catholic education, organizational leadership, and institutional theory, as well as to practitioners charged with preserving mission under conditions of merger, professionalization, and scale