Inequality for All makes an important contribution to current debates about economic inequalities and the growing achievement gap, particularly in mathematics and science education. The authors argue that the greatest source of variation in opportunity to learn is not between local communities, or even schools, but between classrooms. They zero in on one of the core elements of schooling—coverage of subject matter content—and examine how such opportunities are distributed across the millions of school children in the United States. Drawing on data from the third TIMMS international study of curriculum and achievement, as well as a six-district study of over 500 schools across the United States, they point to Common Core State Standards as being a key step in creating a more level playing field for all students. William H. Schmidt is University Distinguished Professor at Michigan State University and co-director of the Education Policy Center. Curtis C. McKnight is emeritus professor of mathematics at the University of Oklahoma.