Many practitioners (and the public) highly value standardizing curriculum and instruction for students. They believe that common standards and instruction will produce equal opportunity--a value dear to most policymakers and educators, and to Americans in general. Yet educators and the public also prize individual excellence. Differentiating the curriculum for students enables schools to customize learning opportunities and cultivate individual achievement. Standards and customization have been battling it out--and compromising--for the past 100 years. In the second decade of the 21st century, reform efforts to both standardize and customize curriculum and instruction present themselves anew. Tensions arise over these competing values because there are insufficient resources in terms of time, money, and people to achieve them. So educators try to reconcile them by embracing one value and holding the other at arm's length for a while or by striking compromises--satisfying one a little by sacrificing the other a little.