Abstract This paper estimates the causal effect of teenage childbearing on educational attainment using two cohorts of Australian twins and their relatives. Our main finding is that the negative effect of teenage childbearing on educational attainment appears to be small. We find no difference in educational attainment between teen mothers and their identical twin sisters. Data on the relatives of the twins enable us to compare a teen mother with both her twin sister and her other sibling sisters. When twin sisters are used as a control group instead of sibling sisters, the estimated difference in educational attainment is much smaller.