Around the world there is a preoccupation with improving the performance of schools and school systems. Comparisons made between countries through PISA and PERLs have led to a preoccupation, and in some cases, an obsession, with securing a high position in the international league tables. The minds of policy-makers and politicians alike are sharply focused on finding effective ways of scaling the international performance ladder and moving ever closer to the elusive top. This article focuses on the potential challenges, complications and considerations for those leading change at scale. The final section of this article considers the fallacies of system improvement, drawing upon the findings of a recent research study of high performing organizations and systems. The author concludes by arguing that the single most important factor in leading successful system-level improvement is capacity building.