It is a widely held view that the best way to improve intergenerational mobility is to provide more equitable distribution of human capital. Our study finds that achievement gaps over the past half century have neither grown nor shrunk; they have remained constant. The analysis behind this conclusion combines four separate student assessments that are each designed to track student performance over time on a consistent basis. The data come from two US government assessments (two versions of the National Assessment of Educational Progress, or NAEP: the Long Term NAEP and the Main NAEP) and two international assessments (Trends in International Mathematics and Science Study, or TIMSS, and the Programme for International Student Assessment, or PISA). Combined, these surveys provide 98 test-year-age observations of student achievement including performance in math, science, and reading for birth cohorts between 1954 and 2001.