We are proposing a multi-faceted study that includes both analyses of nationally representative, longitudinal data as well as an observational study of kindergarten and first grade classrooms for which we will collect original data. These complementary study components will provide one of the most complete pictures of mathematics instructional content in the early school years to date. First, we propose to leverage the two nationally representative, longitudinal studies that have been fielded by the National Center for Educational Statistics to explore mathematics content coverage during the first years of primary school. Using the Early Childhood Longitudinal Studies, Kindergarten Class of 1998-99 (ECLS-K: 1999) and the class of 2010-11 (ECLSK: 2011), we will describe the mathematics content to which children are exposed in kindergarten, first, and second grades, and explore how it differs across years and in different contexts. For the second component of our study, we are proposing to conduct an observational study of kindergarten and first grade math instruction in 24 New York City (NYC) public schools during the fall of 2016 and spring of 2017 which will focus on understanding a) the alignment between Pre-K math instruction and elementary school math instruction in NYC and b) the alignment between the enacted curriculum and the Common Core State Standards in Mathematics for kindergarten (CCSSM). Our primary focus will be on obtaining in-depth information on the quantity, content and quality of kindergarten and first grade mathematics instruction.