We examine trends over time in age-grade retardation in schooling at ages 6 to 17 and in the effects of its demographic and socioeconomic correlates. We estimate a logistic regression model of age-grade retardation with partial interaction constraints using the annual October school enrollment supplements of the Current Population Survey. This model identifies systematic variation in the effects of social background across age and time from 1972 to 2003. While the effects of socio-economic background variables on progress through school become increasingly powerful as children grow older, that typical pattern has been attenuated across the past three decades by a steady, secular decline in the influence of those variables across all ages. A great deal of concern has been expressed about rising levels of economic and social inequality in the United States since the middle 1970s, and about the potential intergenerational effects of such inequality. However, there has been an opposite trend in the effects of social origins on age-grade retardation, which is an important indicators of progress through schooling. A trend is not a law, and there is reason to be concerned about the recent deceleration of the secular decline in effects of social background on age-grade retardation.