This article reconsiders the role of prior academic preparation as it relates to English learners' access to advanced coursework in high school. Using longitudinal data from New York City (n = 178,155), we test a set of interactions between middle school preparation--in the form of math achievement and advanced math and science coursework--and subgroups of English learners (ELs). We find that for all ELs, both components of prior preparation are significantly less predictive of college-preparatory STEM course-taking than for comparable non-ELs. We also find that ELs are less likely to benefit from enrollment in schools where the average prior preparation is higher. These findings problematize the common practice of controlling for prior achievement without permitting the effects to vary by subgroup--an approach that tends to overstate the role of prior academic preparation in explaining course-taking disparities in high school. This study thus provides evidence for a necessary analytic adjustment in a growing area of research, as well as the need for more attention on the high school transition for ELs' access to STEM coursework.