Is teaching an art or a science? It’s a little of both. There is artistry in the way teachers connect with students and foster their understanding. At the same time, there is a science to teaching and learning, an evidence base on which to build our approaches to developing students’ knowledge, skills, and competencies. We know more than ever about students’ learning trajectories and how new learning builds on prior knowledge. Learning is cumulative. Gaps in knowledge and skills become cracks in the foundation of lifelong success. Sadly, only some students in the U.S. have access to rigorous, grade-appropriate content and assignments. A recent study from TNTP found that students from low-income families spent half as much time on grade-appropriate assignments as those from higher-income