In the current educational context, school models that leverage technology to personalize instruction have proliferated, as has student enrollment in, and funding of, such school models. However, even the best laid plans are subject to challenges in design and practice, particularly in the dynamic context of a school. In this collective case study, we identify challenges, disruptions, and contradictions as they occur across schools engaged in implementing technology-mediated personalized learning. Using cultural historical activity theory--a theoretical framework concerned with the individual and contextual factors influencing school change--to frame the analysis, we also examine some of the structural and contextual sources of these disruptions and contradictions. Our findings enable us to offer recommendations for policymakers and for practitioners engaged in implementing personalized learning models, as well as directions for future research on this topic.