Kathy Sylva is Professor of Educational Psychology at the University of Oxford. She has researched extensively in the education and care of young children, with a special interest in the effects of early education and also the role of education in combating social disadvantage. Iram Siraj is Professor of Child Development and Education at the University of Oxford, UK and Research Professor, University of Maynooth, Ireland. She is coauthor of each of the Curriculum, Leadership and Interaction Quality Rating Scales (CLIQRS) and has led several RCTs on effective professional learning. Brenda Taggart is an Honorary Senior Research Associate at University College London Institute of Education. She co-led on the Effective Pre-school, Primary, and Secondary Education (EPPSE 997-2 4). Her background is in teaching and research that explores the impact of educational initiatives. Denise Kingston is Senior Researcher at Oxford University and an Honorary Research Fellow at the University of Sussex. She is a specialist in children's development, with a background in educational psychology. Her research focus is effective professional development and early childhood pedagogy and practice.