Sex education presents a major dilemma for state-minority relations, reflecting a conflict between basic rights to education and religious freedom. In this comparative ethnography of informal sex education among ultra-Orthodox Jews (Haredim) in Israel and England, we frame the critical difference between “age-appropriate” and “life-stage” (marriage and childbirth) models of sex education. Conceptualizing these competing approaches as disputes over “knowledge responsibility,” we call for more context-specific understandings of how educational responsibilities are envisioned in increasingly diverse populations.