The One Child Policy initiated in the late 1970s created a birth cohort with an unusually high proportion of only children. This paper examines the relationship between being the only child in the family and educational attainment, as well as its potential variations by social origin. Drawing my sample from the China Family Panel Studies, I compare two birth cohorts born before and after the birth-control policy. Results show that in the younger cohort, being the only child in the family produces a premium in educational outcomes, including years of completed schooling and odds of progressing through critical grade transitions. In addition, I observe a pattern that the only-child premium tends to be larger for people with higher social origins in competitive grade transitions.