Book excerpt: This book describes the use of data systems in early childhood settings (birth to eight years) for the purposes of assessment, evaluation and curriculum planning. It presents an international collection of research examining ways in which teachers and researchers have revisited notions of what constitutes effective assessment, revised ways in which they assess children’s learning and development and use the knowledge gained for curriculum planning. It offers insights into contemporary research on how teachers and children are engaging with data systems as part of effective assessment and how these approaches influence practice. This book presents recent theorizing and examples of research which have investigated innovative approaches to assessment using data systems in early years settings. It represents both early childhood and junior primary contexts and includes research which focusses on teachers’ perspectives and reflections on use of data systems. It also examines research which reflects on what children gain from being involved in these data systems.