The key to improving student achievement, the author asserts, is to pay attention to child and adolescent development. If this factor is overlooked, new approaches to curriculum, instruction, and assessment will have little chance of succeeding. But even troubled districts that have made development a priority have seen remarkable success. The author argues that many improved practices in education that have been developed over the past two decades have been less successful than they might have been because they have focused primarily on curriculum, instruction, assessment, and modes of service delivery. Insufficient attention has been paid to child and adolescent development. When these matters are addressed at all, the focus is often on the student--on a problem behavior--and not on how to create a school culture that promotes good growth along the six critical developmental pathways: physical (including brain development), social/interactive, psycho-emotional, ethical, linguistic, and cognitive/intellectual.