As the most significant revision of federal education policy in decades, No Child Left Behind Act (NCLB) raises the question of whether it represents a sharp departure from past policy or simply the next phase in the evolution of that policy. This article examines the implementation history of Title I of the Elementary and Secondary Education Act from the original legislation enacted in 1965 to the most recent embodiment in NCLB. It concludes that, although NCLB has expanded federal regulation, this newest version reflects an evolution of the federal role rather than a radical redefinition, with NCLB's design only possible because of profound changes in the state role over the past 20 years.