America's young children are increasingly enrolled in early care and education settings—more than 1.3 million children (28 percent) attended state-funded preschool at age 4 in 2011–121. Accordingly, the field of early childhood has become keenly aware of the importance of high-quality early childhood care and education that aims to promote children's cognitive, linguistic, creative, emotional, social, and physical development. At the same time, school readiness is a hotly debated topic with long-reaching effects on the experiences that children have in early childhood settings. The reality is that some children arrive at elementary school with the foundation to learn to read and engage in mathematics already in place, while others have yet to build a foundation for readiness. Initial readiness differences are powerful predictors for later school achievement, economic productivity, and health2.