Persistent gaps between the academic achievements of different groups of children are thoroughly documented by the U.S. National Assessment of Educational Progress and other statistical analyses of state assessments, grades, course selection, and dropout rates. Despite improvements in some years, the gap endures as a consistent and disturbing phenomenon that contradicts the fundamental belief that any child who studies and works hard, regardless of socioeconomic status, skin color, or country of origin, will succeed in school and in life. And, having acknowledged this contradiction, the question becomes: Where does the responsibility for this failure lie? With the schools? The kids? Their families? The public discourse about reform and the achievement gap is stuck between the grim statistical face of failure and shining stories of success, courage, and charisma in the public schools. How are educators to negotiate this confusing territory, framed by hopeful portraits of successful schools on the one hand, devastating statistical indictments on the other, and the taxing policy environment of NCLB on all sides? This "Infobrief" is the first in a series that will focus on the achievement gap. The intent of the series is to provide guidance for policymakers and practitioners seeking to institutionalize processes that successfully address achievement gap issues. "The Achievement Gap--Closing the Gap: An Overview" seeks first to examine what the gap is, as a statistical construct, and to present what educational research has determined about its many causes, outside of schools as well as within. Such an examination will hopefully lead to a deeper understanding of what is needed to close the gap--namely, a comprehensive set of strategies that consider the whole child: developmental years, physical and emotional health, and supportive family and community structures, as well as schooling issues.