The association between attachment and school-related cognitive functioning was longitudinally examined for a French Canadian sample of 108 school-age children. The affective quality of mother-child interaction patterns, child cognitive engagement, and quality of child attachment to mother were evaluated during a laboratory visit that included a separation-reunion procedure occurring when the children were approximately 6 years of age. Children's mastery motivation and academic performance were assessed 2 years later (at age 8). Analyses indicated that secure children had higher scores than their insecure peers on communication, cognitive engagement, and mastery motivation. Controlling children were at greatest risk for school underachievement, with the poorest performance on all measures except mastery motivation. Avoidant and ambivalent children were lowest on mastery motivation. Results of mediational analyses support the salience of mother-child interactional processes and child cognitive engagement at school age in explaining relations between attachment and cognitive functioning in school.