Flipped lesson planning, as popularized by Bergman & Sams (2012a), has been viewed by many as a revolutionary pedagogy, tailor-made for the twenty-first century classroom. Enthusiasm for flipped lesson planning has out-paced the collection of data that might determine its effectiveness. This paper presents the results of a study that compared the learning outcomes of students who learned a geometry concept from a flipped lesson to students who learn the same concept from a traditionally taught lesson. It also compared students' perceptions of their own learning following a flipped lesson and traditionally taught lesson. Data collected during this study showed no significant differences in the learning outcomes of students who participated in a flipped lesson and students who learned in a traditionally taught lesson. Students who participated in the traditional lesson reported significantly higher satisfaction with their own learning than students who participated in the flipped lesson. These results indicate the complexity of the flipped lesson paradigm invite might invite more research aimed at determining the efficacy of flipped lesson planning in other contexts.