This chapter lays out an argument for why a new approach to understanding children’s development in school is necessary. It first reviews the limitations of research with young children in Head Start programs and elementary schools serving large percentages of children in poverty within the US. These approaches are critiqued in light of findings that challenge the validity and reliability of teacher report and other commonly used measures. Issues of bias and cultural relevance in ways of defining the development of children placed at risk are discussed. Promising insights from research using alternative frames and units of analysis are then contrasted with those of large-scale studies. Finally, the rationale for focusing on collaborative competence as a key driver of development throughout childhood is elaborated. The potential of a developmental sequence of collaboration beginning with preschooler free play and leading into more complex collaborations during elementary school is proposed. Summaries of each chapter and how it contributes to this argument is provided.