The Holistic Equilibrium Theory of Organizational Development was used to gain an in-depth understanding of the influence of holistic staff capacity on conducting effective internal whole-school evaluation (IWSE) within the Gauteng Department of Education's public secondary schools. In the context of South African education, the staff of each public school are legally mandated to conduct an IWSE annually to self-determine their school development paths within a school improvement framework. This IWSE programme, however, takes a myopic unidimensional approach to whole school improvement, demanding public school staff, from diverse milieus with varying degrees of capacity, to take greater ownership of their own development needs through self-evaluative mechanisms. Using a concurrent triangulation mixed methods approach comprising a structured questionnaire, supported by focus group interviews, individual interviews with school principals and open-ended responses, this study elicited data on five distinct but integrated theoretical capacity dimensions: school evaluation, school improvement, collaborative cultures, professional learning communities and transformational leadership. The findings from both data collection strands corroborated the overarching conclusion that development of holistic capacities, transcending a technicist, bureaucratic approach, is more likely to result in the meaningful use of IWSE scaffolding school improvement.