This study tested a hypothesized cascade in which children's insecure representations of the interparental relationship increase their school problems by altering children's cortisol reactivity to stress and their executive functioning. Participants included 235 families. The first of five measurement occasions occurred when the children were in kindergarten (M age = 6 years), and they were followed through the transition to high school. The results indicated that children's histories of insecure representations of the interparental relationship during the early school years were associated with executive functioning difficulties in adolescence (M age = 14 years). This in turn predicted subsequent increases in school adjustment difficulties 1 year later. In addition, elevated cortisol reactivity to interadult conflict mediated the association between early histories of insecurity and subsequent executive function problems in adolescence.