Paul G. LeMahieu is a senior advisor to the president of the Carnegie Foundation for the Advancement of Teaching, on the graduate faculty in education at the University of Hawai'I at Mānoa, and the former superintendent of education for the State of Hawai'i. For the past decade, he has researched and written extensively to develop a field of practice that brings networked improvement science into education to rigorously address persistent problems of equity in performance. Paul Cobb is a professor emeritus at Vanderbilt University. His work focuses on improving the quality of mathematics teaching and student learning on a large scale. He is currently involved in a project that is developing practical measures of key aspects of high-quality mathematics and investigating their use as both measures of and supports for instructional improvement.