Background: Dialogic engagement is instrumental in promoting higher-order thinking, motivation, and learning. Despite their dramatic uptake in the US in the past decade, there is limited evidence that online high school courses offer sufficient opportunities for students to communicate and collaborate with teachers and peers. Objectives: This two-part study explores teacher perspectives and the experiences of students in online learning environments to determine if, how, and why students engage in two forms of dialogic engagement–academic discourse and peer collaboration. Methods: To identify the extent to which teachers perceive academic discourse and peer collaboration to be valuable and feasible in online learning environments, Study 1 surveyed educators and advisors of online learning programs (n = 49). To determine whether these perspectives align with student experiences, Study 2 included a series of over-the-shoulder observations of five high school students engaging in their online coursework. Results and Conclusions: Findings reveal a disconnect between best practices in education and reality. Online teachers report that academic discourse is valuable and feasible, but also detail several challenges to successful implementation in online coursework. At the same time, direct observations of high school students indicate that they rarely, if ever, engage in peer collaboration and academic discourse activities. Major Takeaways: Although valued as a means to improve educational outcomes, opportunities for dialogic engagement are not translating to online learning environments. The solution is to develop curriculum, policies, and procedures that centre on meaningful integration of dialogic activities, motivating students to engage.