Both federal and state governments regulate the quality and curricula of early childhood education programs in hopes of promoting the school readiness of disadvantaged children. We draw on data from the experimental Preschool Curriculum Evaluation Research Initiative Study to provide an aggregated look at the impacts of four types of preschool curricula (literacyfocused, math-focused, whole-child and locally developed) on classroom processes as well as children's academic and socioemotional outcomes. The math curriculum included in the study boosted both classroom math activities and children's math achievement relative to the two whole-child curricula (HighScope and Creative Curriculum) found in most Head Start and pre-K classrooms. Also relative to HighScope and Creative Curriculum, the literacy curricula increased early literacy achievement despite producing no statistically significant differences in classroom activities or teacher-child interactions. Although Creative Curriculum produced much more positive classroom processes than locally developed curricula, it failed to improve either the academic achievement or behavior of preschool children relative to the local curricula. Implications for Head Start and pre-K curricula choice and the utility of widely used classroom rating scales are discussed. ! ! 2 Boosting School Readiness with Preschool Curricula ! ! 3Prominent alternatives (or supplements) to whole-child curricular approaches target specific skills, typically literacy or numeracy. In contrast to whole-child curricula, these curricula assume that children benefit most from sequenced, explicit instruction intended to promote skills in a specific content area -typically literacy, math, or socio-emotional skills. Consistent with whole-child approaches, most of these academic-skill curricula include both large and small group activities and also provide opportunities for free play and exploration Wasik & Hindman, 2011).Given the wide array of choices available to policymakers, it is important to determine the comparative effectiveness of different types of curricula in promoting school readiness, a task that few studies have attempted. Our analysis uses data from the Preschool Curriculum Evaluation Research Initiative Study (PCER, 2008), a large multi-site random-assignment experimental study focused on a diverse set of preschool curricula, to investigate whether the type of curricula four-year olds experience differentially affects the development of their math, literacy, and socioemotional skills. Our data also provide a look into the black-box of classroom processes targeted by early childhood education quality assessment initiatives, which enables us to assess whether the curricula impact the nature of classroom activities and the warmth of teacher-child interactions.We find that the math curriculum included in the study is more effective at boosting both classroom math activities and children's math skills than are the "whole-child" curricula most often used in Head Start and pre-K classrooms (Crea...