Yizhen Huang, Eric Richter, Thilo Kleickmann, Dirk Richter

• Teachers frequently express stress associated with teaching in large classrooms. Despite the timehonored tradition in teacher stress research of treating class size as a job-related stressor, the underlying premise that class size directly impacts teachers' stress reactions remains untested. In this randomized controlled experiment targeted at preservice teachers, we utilized a standardized virtual reality (VR) classroom to examine whether class size (number of student avatars) directly affected physiological (heart rate) or psychological (subjective rating) stress reactions among 65 preservice teachers. Results from linear mixed-effects modeling (LMM) showed that class size significantly predicted both their physiological and psychological stress reactions in the simulated environment: Average heart rate and subjective stress ratings were both significantly higher in the large class size condition. Further investigations into the causes of this association has been proposed. These findings may contribute to a better understanding ofTeachers frequently express stress associated with teaching in large classrooms. Despite the timehonored tradition in teacher stress research of treating class size as a job-related stressor, the underlying premise that class size directly impacts teachers' stress reactions remains untested. In this randomized controlled experiment targeted at preservice teachers, we utilized a standardized virtual reality (VR) classroom to examine whether class size (number of student avatars) directly affected physiological (heart rate) or psychological (subjective rating) stress reactions among 65 preservice teachers. Results from linear mixed-effects modeling (LMM) showed that class size significantly predicted both their physiological and psychological stress reactions in the simulated environment: Average heart rate and subjective stress ratings were both significantly higher in the large class size condition. Further investigations into the causes of this association has been proposed. These findings may contribute to a better understanding of the effects of classroom features on preservice teachers' emotional experiences and well-being.…