This article describes basic facts regarding the Black-White test score gap over the first four years of school. Black children enter school substantially behind their White counterparts in reading and math, but including a small number of covariates erases the gap. Over the first four years of school, however, Blacks lose substantial ground relative to other races; averaging 0.10 standard deviations per school year. By the end of third grade, there is a large Black-White test score gap that cannot be explained by observable characteristics. Blacks are falling behind in virtually all categories of skills tested, except the most basic. None of the explanations we examine, including systematic differences in school quality across races, convincingly explain the divergent academic trajectory of Black students.