This handbook is meant to be a resource for anyone interested in research, practice, or policy in the field of K-12 online and blended learning. This book is not intended to be a collection of opinions on the field. Nor is it meant to be a compendium of the top research articles for this past year. It is not a list of what is currently trending in K-12 online and blended schools. And, it is not a list of ‘best pieces’ from leading researchers in the field. Rather, this handbook is a collection of what we currently know about research in the field.