Teacher burnout is a critical public health problem. In 2022, 90% of teachers reported burnout as a serious issue. Teacher burnout contributes to poor educational outcomes for students and poor health and work outcomes for teachers. Previous literature on teacher burnout has underrepresented certain populations, such as public middle school teachers who teach a core classroom subject. Therefore, the purpose of this dissertation was to explore the factors that contribute to burnout and its consequences for public, core-classroom middle school teachers in the U.S. This cross-sectional design was conducted using survey data collected from a nonprobability sample of 200 public middle school teachers across the U.S., with burnout levels assessed using the Maslach Burnout Inventory-Educator Specific. In manuscript 1, the Job Demands-Resources (JD-R) model was applied as a theoretical framework for path analysis of job demands (e.g., workload, student misbehavior, work to nonwork and nonwork to work conflict) and job resources (e.g., administrative and coworker support, teaching efficacy) to predict burnout levels among teachers. Job demands, such as high workload, nonwork to work and work to nonwork conflicts, had positive associations with teacher burnout. The study also explored sex differences, revealing that female teachers experienced higher workloads, more frequent work-life conflicts, and greater student misbehavior compared to male teachers, although burnout indicators did not differ between sexes. In manuscript 2, regression analyses were conducted to assess relationships between teachers' reported burnout and their productivity, job satisfaction, stress, and mental and physical health. Depersonalization predicted poor mental health and decreased productivity, while personal accomplishment predicted job satisfaction. Emotional exhaustion did not predict mental, physical, or workplace outcomes. Female teachers reported more days of poor mental health and stress than male teachers. Additionally, 6th and 9th grade teachers differed in their measures of mental and physical health, productivity, and stress. The findings here confirm the need for interventions at multiple levels to prevent burnout, support teacher well-being, and reduce burnout's negative consequences when it occurs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]