The Common Core State Standards (CCSS) of 2010 represent a new chapter in the 25-year history of standards-based reforms (SBR). The CCSS attempts to bring the system back to the principles of its founding--more rigorous, focused, academic content and performance expectations collectively embraced by the nation. The new standards depart significantly from existing practice, especially in their high level of cognitive demand, topical range, and curricular sequencing. In this article, we explore what decades of experience have shown about alignment to standards. Most conceive of alignment as a relatively simple technical task of matching curriculum and other tools to the standards. This is a necessary, but only a first, step, and one that is more complex than often imagined. To achieve the far-reaching institutional changes envisioned by SBR, additional and intensive work is necessary to align system incentives, as well as classroom instruction.