We take Gary Becker's child quantity-quality trade-off hypothesis to the historical record, investigating the causal link from family size to the literacy status of offspring using data from Anglican parish registers, c. 1700-1830. Extraordinarily forhistorical data, the parish records enable us to control for parental literacy, longevity and social class, as well as sex and birth order of offspring. In a world without modern contraception and among the couples whose children were not prenuptially conceived we are able to explore a novel source of exogenous variation in family size: marital fecundability as measured by the time interval from the marriage to the first birth. Consistent with previous findings among historical populations, we document a large and significantly negative effect of family size on children's literacy.