Multi-user mixed reality (MR) holds great potential for classroom based teaching, but what are the most effective teaching experiences, formats and pedagogical techniques for this emerging technology? Through a series of case studies involving four professors and their students, we explore the pedagogical potential of headsetbased co-located MR. Using a custom platform, a series of immersive lectures were developed and delivered covering a range of themes, each including a structured design process, live immersive lectures with students and post-lesson interviews and analysis. From these experiments emerged a common set of educational possibilities offered by the medium, including spatiotemporal narratives, direct and joint attention, virtual travel, collaborative interaction and spatial thinking. Key challenges facing the adoption of MR in educational settings were also identified. This work demonstrates an effective method for exploring the possibilities of MR and provides insights for educators, researchers and developers interested in integrating MR into educational settings.