The purpose of this large-scale, multi-year, national study is to determine whether some early elementary school math curricula are more effective than others at improving student math achievement, thereby providing educators with information that may be useful for making adequate yearly progress. The main questions being addressed by the study are: (1) What are the relative effects of different early elementary school math curricula on student math achievement in disadvantaged schools?; (2) Under what conditions is each math curriculum most effective?; (3) What is the relationship between teacher knowledge of math content/pedagogy and the effectiveness of the curricula?; and (4) Which math curricula result in a sustained impact on student achievement? The study is addressing these questions by examining the relative effects of four diverse curricula, by recruiting schools without prior experience using the study's curricula, having publishers provide schools and teachers with curriculum materials and training, and evaluating the effects of the curricula (including materials, training, content, and pedagogy) on student achievement.