This article reports findings from qualitative research conducted in 17 New York City schools to better understand why many school leaders--particularly principals--have recently dismantled their school's bilingual education programs, as part of a significant citywide trend during a restrictive period in US language policy. A main finding is that principals, who are called upon to determine their school's language policy, have not received any formal preparation to do so. New York, like most states, does not require any coursework on the education of emergent bilinguals for the certification of administrators. The school leaders we interviewed who had eliminated their bilingual programs hold limited understandings of bilingualism, linguistic diversity, and bilingual education. By contrast, principals who have maintained their bilingual education programs were found to be well prepared to serve emergent bilinguals and strongly believe in the benefits of bilingual education. They also advocate for bilingual education and protect their school's programming choices in the face of English-only pressures. Based on our findings, we argue that principals are particularly crucial to the survival and success of bilingual education. What is more, we argue that all school leaders serving emergent bilinguals would benefit from specialized preparation to educate this student population.