Although school is only one of many places where youths write, the writing privileged in school is often upheld as standard, whereas adolescents' out-of-school writing often uses forms, styles, and topics not taught or allowed in school. Little is known about how K-12 educators can use research on out-of-school writing to inform in-school writing curricula. The author examined research on adolescent out-of-school writing to synthesize the literacy field's knowledge of this phenomenon. The empirical literature from the last decade documents out-of-school writing that provides opportunities to focus on writing as a craft, includes digital texts and participatory cultures, emphasizes meaningful purposes and audiences, and highlights the work done by marginalized writers. The discussion considers implications for the conception of literacy writ large and offers principles drawn from existing scholarship as implications for K-12 writing educators.