Despite federal and state laws and regulations that require states and local districts to provide English language learners (ELLs) with support services, prior research has indicated that ELLs are, in general, lagging behind non-ELLs in academic achievement. An unanswered question is whether the initial designation of students as ELL influences their later academic achievement and how. Using a regression discontinuity design, this study compares the outcomes for students near the cutoff for being initially classified as ELL and initially fluent English proficient (IFEP) students. Among students near the cutoff, the classification had significant positive effects on ELLs' academic achievement in elementary grades and, to some extent, in the later grades.