The recent emergence of updated learning standards in science and mathematics, coupled with increasingly diverse school students across the nation, has highlighted the importance of updating professional learning opportunities for science and mathematics teachers. One promising approach that has emerged is the use of simulations to engage teachers in approximations of practice where the focus is on helping them learn how to engage in ambitious content teaching. In particular, recent technological advances have supported the emergence of new kinds of digital simulations and have brought increased attention to simulations as a tool to enhance teacher learning. This project will develop and implement a working conference for scholars and practitioners to articulate current use cases and theories of action regarding the use of simulations in PreK-12 science and mathematics teacher education. The conference will be structured to provide opportunities for attendees to share their current research, theoretical models, conceptual views, and use cases focused on the design and use of digital and non-digital simulations for building and assessing K-12 science and mathematics teacher competencies. This project is funded by the Discovery Research preK-12 program (DRK-12) that seeks to significantly enhance the learning and teaching of science, technology, engineering and mathematics (STEM) by preK-12 students and teachers, through research and development of innovative resources, models and tools. Projects in the DRK-12 program build on fundamental research in STEM education and prior research and development efforts that provide theoretical and empirical justification for proposed projects. <br/><br/>While the use of simulations in teacher education is neither new nor limited to digital simulation, emerging technological capabilities have enabled digital simulations to become practical in ways not formerly available. The current literature base, however, is dated and the field lacks clear theoretic models or articulated theories of action regarding what teachers could or should learn via simulations, and the essential components of effective learning trajectories. This working conference will be structured to provide opportunities for attending, teacher educators, researchers, professional development facilitators, policy makers, preservice and inservice teachers, and school district leaders to share their current research, theoretical models, conceptual views, and use cases regarding the role of simulations in K-12 science and mathematics teacher education. The conference will be organized around four major goals, including: (1) Define how simulations (digital and non-digital) are conceptualized, operationalized, and utilized in K-12 science and mathematics teacher education; (2) Document and determine the challenges and affordances of the varied contexts, audiences, and purposes for which simulations are used in K-12 science and mathematics teacher education and the variety of investigation methods and research questions employed to investigate the use of simulations in these settings; (3) Make explicit the theories of action and conceptual views undergirding the various simulation models being used in K-12 science and mathematics teacher education; and (4) Determine implications of the current research and development work in this space and establish an agenda for studying the use of simulations in K-12 science and mathematics teacher education. The project will produce a white paper that presents the research and development agenda developed by the working conference, describes a series of use cases describing current and emergent practice, and identifies promising directions for future research and development in this area. Conference outcomes are expected to advance understanding of the varied ways in which digital and non-digital simulations can be used to foster and assess K-12 science and mathematics teacher competencies and initiate a research and development agenda for examining the role of simulations in K-12 science and mathematics teacher education.<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.