Objectives: To assess the rate of COVID-19 among in-person K-12 educators and its association with various COVID-19 prevention policies in school districts. Methods: Actively working, in-person K-12 educators in Wisconsin were linked to COVID-19 cases with onset during September 2–November 24, 2021. A mixed-effects Cox proportional hazards model, adjusted for pertinent person- and community-level confounders, compared the hazards rate of COVID-19 among educators working in districts with and without specific COVID-19 prevention policies. Results: In-person educators working in school districts that required masking for students and staff experienced 19% lower hazards of COVID-19 compared with those in districts without any masking policy (hazards ratio = 0.81, 95% confidence interval = 0.72 to 0.92). Reduced COVID-19 hazards were consistent and remained statistically significant when educators were stratified by elementary, middle, and high school environments. Conclusions: In Wisconsin’s K-12 school districts, during the Fall 2021 academic semester, a policy that required both students and staff to mask was associated with significantly reduced risk of COVID-19 among in-person educators across all grade levels.