The purpose of this study is to understand how a policy that provided college-prep coursework for low-skill students may affect instructional organization within schools, and how such effects on instructional organization may have unintended consequences on academic outcomes of high-skill students who were not targeted by the policy. The author and her colleagues focus on a ninth-grade algebra-for-all policy implemented in Chicago public schools (CPS) and address two research questions; (1) to what extent did a policy that required algebra for all students in ninth grade affect classroom academic composition?; and (2) for high-skill students who were not targeted by the policy, how did the policy affect their academic outcomes? The results showed potential challenges of a curricular policy of expanding a college-prep curriculum to all students: schools are likely to detrack math classrooms when the policy merely required them to eliminate remedial coursework, and this resulted in lower peer ability levels for high-skill students. Consequently, their test scores suffered from this policy. This study suggests that simply mandating a college-prep curriculum for all students is not sufficient enough to improve academic outcomes of all students. An appendix presents: Statistical Models to estimate the effect of an algebra-for-all policy on students' academic outcomes among high-skill students. (Contains 3 tables and 11 figures.)