John Hattie, Ph.D., is an award-winning education researcher and best-selling author with nearly 30 years of experience examining what works best in student learning and achievement. His research, better known as Visible Learning, is a culmination of nearly 30 years synthesizing more than 1,500 meta-analyses comprising more than 90,000 studies involving over 300 million students around the world. He has presented and keynoted in over 350 international conferences and has received numerous recognitions for his contributions to education. His notable publications include Visible Learning, Visible Learning for Teachers, Visible Learning and the Science of How We Learn, Visible Learning for Mathematics, Grades K-12, and, most recently, 10 Mindframes for Visible Learning. Klaus Zierer is Professor of School Education at the University of Augsburg, Germany. He taught for five years in primary and secondary schools. In 2009 he was a Visiting Research Fellow at the Department of Education, University of Oxford. He is currently an Associate Research Fellow of the ESRC Centre on Skills, Knowledge and Organisational Performance (SKOPE). His research interests include international aspects of school education, learning and teaching, teacher education and professionalisation.