The purpose of this study was to explore high school physical education students' usage and perceptions of a supplemental online health-related fitness knowledge curriculum through the lens of the Unified Theory of Acceptance and Use of Technology. Individual interviews were conducted with 37 students who were enrolled in a ninth-grade physical education class. The course used an externally provided online curriculum designed to deliver and assess health-related fitness knowledge. Initial themes were generated using open and axial coding compiled into a codebook. The codebook was pilot-tested and finalized following peer debriefing sessions. Four main themes were developed: "Home(room), Alone"; "Easy to Use, Easier to Ignore"; "Disconnected and Conflicted"; and "Low Value, Low Priority." Students completed their online work alone, but location and devices varied. Most thought the online platform was easy to navigate, and many completed multiple modules at once. Students sensed that the online content was disconnected from face-to-face physical education and questioned why they were required to engage in sedentary online learning for a physically active course. They also expressed difficulty understanding the value of the online content and assigned a low priority to completing it as a result. Implementing a supplemental online physical education curriculum presents challenges given the relative novelty of the modality within the subject. This study highlights the important role system design plays in the online learning process. It also illustrates the responsibility teachers have in helping students see the value of online learning opportunities by making connections to their own lives.