In a context characterized by the dual issues of educational inequality and problems with fertility, the internal relationship between these two factors requires further in-depth exploration. On the basis of data drawn from the China Family Panel Studies (CFPS) from 2010 to 2018, this paper investigates whether “super high schools” in cities represent a form of educational inequality, uses a combination of a two-way fixed effect model with the instrumental variable method to discuss the influence of this situation on family fertility and the corresponding transmission mechanism, develops a proportional risk regression model, and expands our understanding of the influence of educational inequality on the second-child birth interval. This study reveals that educational inequality significantly suppresses the number of family births and that the paths of action associated with this effect include both the explicit and implicit costs of education. The inhibitory effect of educational inequality on the number of family births varies according to urban grade, urban or rural classification, and the education levels attained by women. In addition to decreasing the number of family births, educational inequality increases the second-child birth interval. This paper not only enriches related research on family multichild behavior but also provides an educational reference for attempts to address the issue of continuously low fertility rates in China and establish a connection between population and educational economics.