In teacher education it is widely acknowledged that learning to teach requires that preservice teachers have robust, authentic, and consistent opportunities to engage in the work of teaching--ideally across different contexts, with diverse student populations, and for varied purposes--as they hone their instructional practice. Practice teaching experiences in K-12 classrooms, such as field placements and student teaching, are the most widely used approaches to provide these opportunities. In an ideal world these experiences are opportunities for preservice teachers to observe and work closely with mentor teachers and try out new instructional strategies with individual, small groups, and whole classes of K-12 students. While these experiences are critical to supporting preservice teachers’ learning, it can be difficult to help preservice teachers transition from university classrooms to field placements in ways that provide them with opportunities to enact ambitious instructional strategies. This need is particularly acute in mathematics and science education, where classrooms that model strong disciplinary discourse and argumentation are not always prevalent. This challenge is amplified by the COVID-19 pandemic environment; with schools and universities across the nation operating online, many preservice teachers will miss out on opportunities to practice teaching both within their courses and in K-12 classrooms. To address this urgent challenge in STEM education, project researchers will develop, pilot, and refine a set of coordinated and complementary activities that teacher education programs can use in both online and face-to-face settings to provide practice-based opportunities for preservice teachers to develop their ability to facilitate argumentation-focused discussions in mathematics and science, a critical teaching practice in these content areas. The practice-based activities include: (1) interactive, online digital games that create targeted practice spaces to engage preservice teachers to respond to students’ content-focused ideas and interactions; (2) facilitating group discussions with upper elementary or middle school student avatars in a simulated classroom using performance-based tasks; and (3) an immersive virtual reality whole-classroom environment that allows for verbal, textual and non-verbal interactions between a teacher avatar and 24 student avatars. The online practice suite, made up of these activities along with supports to help teacher educators use them effectively, represents not just an immediate remedy to the challenge of COVID-19, but a rich and flexible set of resources with the potential to support and improve teacher preparation well beyond the COVID-19 challenge.<br/><br/>This study will use design-based research to create this integrated system of practice teaching opportunities. This approach will involve developing and refining the individual practice activities, the integrated online practice suite, and the teacher educator support materials by working with a teacher educator community of practice and engaging up to 20 teacher educators and 400 preservice teachers in multiple rounds of tryouts and piloting during the three-year project. The project will proceed in three phases: a first phase of small-scale testing, a second phase trying the materials with teacher educators affiliated with the project team, and a third phase piloting materials with a broader group of mathematics and science teacher educators. Data sources include surveys of preservice teachers’ background characteristics, perceptions of the practice activities, beliefs about content instruction, perceptions about preparedness to teach, and understanding of argumentation and discussion, videos and/or log files of their performances for each practice teaching activity, and scores on their practice teaching performances. The project team will also observe the in-class instructional activities prior to and after the use of each practice teaching activity, conduct interviews with teacher educators, and collect instructional logs from the teacher educators and instructional artifacts used to support preservice teachers’ learning. Data analysis will include pre and post comparisons to examine evidence of growth in preservice math and science teachers’ beliefs, perceptions, understanding, and teaching performance. The project team will also build a series of analytic memos to describe how each teacher educator used the online practice suite within the mathematics or science methods course and the factors and decisions that went into that each use case. Then, they will describe and understand how the various uses and adaptations may be linked to contextual factors within these diverse settings. Findings will be used to produce empirically and theoretically grounded design principles and heuristics for these types of practice-based activities to support teacher learning.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.