The article presents findings from a multisited ethnography in two public high schools in Los Angeles and New York City. Schools were chosen for their hyper-diverse student populations. Students came from over 40 countries, speaking 20 languages in one school and 33 languages in another. Results of analysis found that despite contrasting missions, policies, organizational structures, curricular techniques, and teachers' beliefs and attitudes across schools, youths' practices were similar. Youth enacted explicit transcultural repertoires of practice: multiplicities of talking, thinking, and acting that engaged the resources and opportunities of ethnically and linguistically diverse classrooms. The article theorizes the importance of recognizing hyper-diversity as a distinct cultural context that shapes and situates youths' practices and therefore their opportunities to learn.