This paper reports on findings from a five-teacher, exploratory case study, critically observing their implementation of a technology-intensive, augmented reality (AR) mathematics curriculum unit, along with its paper-based control. The unit itself was intended to promote multiple proportional-reasoning strategies with urban, public, middle school students. The researcher used lesson transcripts, observation field notes, and teacher electronic journals, along with pre-/post-interviews and pre-observations to examine differences in implementation between the AR and Control versions of the unit. The author observed less mathematical substance and more adaptations to structure and quality during the AR implementations. In addition to uncovering some significant limitations with AR as it is currently utilized, this study also addresses gaps in the technology literature. Criticism of technology literature includes the fact that it does not consider the effects of teacher and curricular factors on technology-based curricular interventions. By closely examining the implementation of one augmented-reality based, mathematics curriculum, this research provides insights about how and why such curricula become transformed in the classroom. (Contains 3 footnotes, 8 tables, and 6 figures.)