The significant growth of charter schools in the United States has brought both praise for the excellent results achieved by some schools and criticism that charter schools may not be serving the most disadvantaged students. In New York City and elsewhere, a significantly smaller proportion of students enrolled in charter schools are classified as English language learners (ELL) than in traditional public schools. This observation has produced considerable discussion and some policy responses. This paper uses longitudinal student-level enrollment data to explain the ELL gap between New York City charter and traditional public schools. Key findings include: (1) The ELL gap "does" indeed exist; (2) The ELL gap is "not" primarily due to the movement of students with existing ELL classifications across the charter and traditional public school sectors, or out of New York City entirely; (3) The vast majority of the ELL gap is, instead, explained by the fact that ELL students are far less likely to apply to attend charter schools in gateway grades than non-ELL students; and (4) Charter schools declassify a significantly larger proportion of their ELL students than do traditional public schools.