How do schools maintain momentum with change and enter new cycles of growth when they are attempting to do things differently? This article draws on a two-year evaluation of the "Positive Behaviour for Learning School-Wide" initiative to identify key factors that enabled schools to engage in a long-term and iterative change process. Fullan's systems-thinking ideas about school leadership and change, along with literature on the sustainability of educational initiatives, are used to analyse the interrelated factors that assisted schools to successfully embed this new initiative and address challenges. The design features of "School-Wide," the way in which support for schools was organised, and practices within schools that created a continuous improvement culture, all contributed to schools being able to maintain a change momentum and continue to grow "School-Wide" in the longer-term.