This study examined whether the negative association between children's attention difficulties and their academic functioning is largely confined to children whose attention problems persist across early grades and whether it depends on when attention problems emerge in children's schooling.Children from the normative sample of the Fast Track study were classified into four attention problem groups based on the presence versus absence of attention problems in first and second grade.Those with attention problems in both grades showed a decline in reading and math achievement during the K-5 interval relative to children with attention problems in first grade only. Both groups of inattentive first graders also performed worse than comparison children. In contrast, children whose attention problems emerged in second grade did not differ from comparison children on any achievement outcome performed significantly better than inattentive first graders.The implications of these findings are discussed.