This paper employs a large representative sample of Baltimore first graders to examine the effects of various household configurations on children's cognitive performance. Separate analyses are presented for blacks and whites. Using a school process model that is similar to those employed at the secondary level, the analyses show that household composition has an important influence on teachers' marks, particularly reading. These effects are pronounced and most consistent for blacks. The presence of a second adult, not just the father, has beneficial effects on reading marks. Households exert their effects on end-of-first grade achievement primarily by way of parent expectations for reading marks. There is also evidence that household configurations exercise some influence on spring achievement test scores for blacks in both the verbal and the quantitative domains, but stronger in the verbal domain. These effects, in general, are smaller than those for teachers marks.