Maternal education captured at a single time point is commonly employed as a predictor of a child's cognitive development. In this article, we ask what bearing the acquisition of additional qualifications has upon reading performance in middle childhood. This was a secondary analysis of the United Kingdom's Millennium Cohort Study, a cohort of 18,000 children born in 2000. Our outcome variable was Single-Word Reading from the British Abilities Scales at 7 years. Predictors included maternal age and education, relative poverty, and parity. Increasing maternal education over time was associated with improved child outcomes, with a 2-month developmental advantage for children whose mothers had increased education over those whose mothers had not. Parity was important but conditional on this, and there was no evidence of child attainment reducing for the children of older mothers. A time-varying education-level model is consistent with an input-quality mechanism for language development.