"If I've learned anything from the Visible Learning research," writes noted researcher John Hattie, "it's that almost everything in education works. The key question is not, What works? but, Is it working sufficiently above the average of all possible influences? Research has shown above-average effects for leaders who believe their major role is to evaluate their impact, who get everyone in the school working together to understand and evaluate their impact, who learn in an environment that privileges high-impact teaching and learning, who are explicit with teachers and students about what success looks like, and who set appropriate levels of challenge and never retreat to just "do your best." High-impact instructional leaders seek their colleagues' agreement about what constitutes convincing evidence of above-average impacts on student learning. The process of clarifying what counts as evidence and then using that evidence as a guide for deciding which interventions to keep and which to drop is no easy task, especially when pet projects turn out not to be having the desired effect. It all requires strong leadership driven by a relentless determination to maximize the impact on student learning, improve the nature of the evidence about that impact, and make the right decisions going forward.