In an era of increased emphasis on student achievement, school readiness at school entry has become an important part of students' educational trajectories. Thus, the primary aim of this study, guided by theoretical perspectives from across the social sciences, is to identify whether sociodemographic disparities in cognitive and non-cognitive school readiness have decreased, increased, or remained stable over time. Comparing cohorts of students enrolled in kindergarten in 1998-1999 to those enrolled in 2010-2011, I examine within group rates of change over time in teacher-rated math proficiency, verbal proficiency, and approaches to learning, as indicators of school readiness. I compare these rates between groups to assess whether disparities observed between groups in 1998-1999 remain in 2010-2011. (author abstract)