After more than 20 years of vague reference to the principal as instructional leader, progress is finally being made, and the specificity and results are truly awesome. In 1989, William Smith and Richard Andrews wrote a monograph titled "Instructional Leadership: How Principals Make a Difference." In their study of 1,200 school principals, they found that effective principals are engaged in four areas of strategic interaction with teachers: as resource provider, as instructional resource, as communicator, and as visible presence. As valid as these findings still are, they had no sticking power because they failed to lead to practical action on any scale. But now people know specifically what being an instructional leader looks like. The author and his colleagues in Ontario, Canada, and elsewhere have been working with various systems, bringing about impressive reforms on an ever larger scale and with ever greater precision and practicality. The author presents two case examples that demonstrate clearly what this new work looks like and reveal six features that stand out as essential to principals in their efforts toward school reform. He discusses the essence of a principal's power and describes six steps to take to move theory to practice in organizational change. From practice to theory, from doubt to conviction, the key to the speed of quality change is embedded in the power of the principal helping to lead organization and system transformation.