The prevalence of childhood overweight and obesity increased dramatically in the United States during the past three decades. This increase has adverse public health implications, but its implication for children's academic outcomes is less clear. This paper uses data from five waves of the Early Childhood Longitudinal Study-Kindergarten to examine how children's weight is related to their scores on standardized tests and to their teachers' assessments of their academic ability. The results indicate that children's weight is more negatively related to teacher assessments of their academic performance than to test scores. (Contains 1 figure and 6 tables.)