This issue brief analyzes the research on early education. First, it will present and contextualize the arguments made by early-education advocates and the research used to support those arguments. Then it will review other studies that are frequently elided or ignored but that are more relevant to contemporary policy debates. These studies present a consistent pattern: while early education can be a profound boon for deeply disadvantaged students, it can also set disadvantaged students further back and potentially do lasting harm to students born into middle-class families. (author abstract)