In some American schools, about a fifth of the fathers have spent time in prison during their child's primary education. We examine how variation across schools in the aggregation and concentration of the mass imprisonment of fathers is associated with their own children's intergenerational educational outcomes and "spills over" into the attainments of other students. We assess the association of this interinstitutional and intergenerational "prison through school pathway" with downward and blocked educational achievement. Educational and economic resources and other predisposing variables partially explain school-linked effects of paternal imprisonment on measures of children's educational outcomes. However, we find that the net negative school-level association of paternal imprisonment with educational outcomes persists even after we introduce school- and individual-level measures of a wide range of mediating processes and extraneous control variables. We discuss paternal imprisonment as a form of "marked absence." The significance of elevated levels of paternal imprisonment in schools is perhaps most apparent in its negative association with college completion, the educational divide that now most dramatically disadvantages individuals and groups in American society. (Contains 6 tables and 1 figure.)