The Common Core State Standards (CCSS) were developed through an unprecedented, state-led initiative that drew on the expertise of teachers, parents, administrators, researchers and content experts from across the country. The Standards define a staircase to college and career readiness, building on the best of previous state standards in English language arts/literacy and mathematics and evidence from international comparisons and domestic reports and recommendations. Three core shifts in literacy and math, deeply grounded in the new standards themselves, offer ways to focus implementation on the few things that bring the most significant return for students. These shifts should guide all aspects of implementing the CCSS--including professional development, assessment design, and curriculum. Education leaders from state boards to building principals must now act to make the new standards a reality in classrooms. By describing these three core shifts, the authors aim to ensure that expectations for teaching and learning are clear, consistent, and tightly aligned to the goals of the Common Core standards themselves. (Contains 6 endnotes.)