Across the United States, students who are deemed not to be proficient in English are classified as English learners (ELs). This classification entitles students to specialized services but may also result in stigmatization and barriers to educational opportunity. This article uses a regression discontinuity design to estimate the effect of EL classification in kindergarten on students' academic trajectories. Furthermore, it explores whether the effect of EL classification differs for students in English immersion versus bilingual programs. I find that among language-minority students who enter kindergarten with relatively advanced English proficiency, EL classification results in a substantial negative net impact on math and English language arts test scores in Grades 2 through 10. This effect, however, is concentrated in English immersion classrooms.