This report examines the importance and efficacy of oral language, literacy, mathematics, and science preschool curricula and how these curricula can be improved through alignment with research on early childhood development and learning. Detailed, research-driven recommendations are presented for what preschool-aged children should be learning in each of these four content areas. The report provides guidance on developmentally appropriate accomplishments for pre-k children, effective instructional practices, components of a strong curriculum, and working with English language learners. The report is intended to offer useful guidance to practitioners and policymakers as they strive to improve preschool quality, generally, and the quality of the preschool experiences offered to poor children, in particular. (Contains 69 notes and lists of suggested readings and useful websites.)