The first 5 years of life are critical for the development of language and cognitive skills.1 By kindergarten entry, steep social gradients in reading and math ability, with successively poorer outcomes for children in families of lower social class, are already apparent.2 — 4 Early cognitive ability is, in turn, predictive of later school performance, educational attainment, and health in adulthood5 — 7 and may serve
as a marker for the quality of early brain development and a mechanism for the transmission of future health inequalities.8 Early life
represents a time period of most equality and yet, beginning with in utero conditions and extending through early childhood, a wide range of socially stratified risk and
protective factors may begin to place children on different trajectories of cognitive development.9, 10