The development of the ISLLC (Interstate School Leader Licensure Consortium) in 1996 was a milestone in helping states and school districts define how leaders can positively influence learning and establishing guidelines to ensure that they do so. More than 40 states have since adopted the ISLLC standards or used them as the basis for their own standards. In many of those states, the standards are playing an important role in informing key policies affecting the training, licensing, induction, professional development and evaluation of school leaders. With Wallace support, these guidelines have been revised by the Council of Chief State School Officers, applying the growth in knowledge about effective leadership practices over the last decade. This publication spells out the changes and their significance for improving leadership policy and practice.