Differentiation is an instructional practice teachers employ to modify their classroom content, process, and products based on student readiness, interest, and learning profile. Many school districts recognize the benefits of differentiated instruction and thus mandate allotted classroom time for its implementation. In this paper, we investigate how teachers in one such district resolved differentiation policy to practice in a high-stakes testing environment. We found, during the designated time for differentiation, teachers regularly remediated small groups but did not similarly address the academic needs of advanced students, thus not enacting the disciplinary standard for differentiation. We suggest teachers are recoupling practice and policy but misaligning it to the disciplinary definition of differentiation, which we contend has broader implications for instructional policymaking. [This is the online first version of an article published in "Educational Policy."]