To educate students while mitigating the spread of COVID-19 during the fall of 2020, schools across the country used different operational approaches, ranging from fully remote instruction to fully in-person instruction with various “hybrid” approaches in between. This report was prepared for the Pennsylvania Department of Education (PDE) to determine whether there is evidence that districts using hybrid approaches (alongside precautions such as mask-wearing and physical distancing) can successfully mitigate in-school virus transmission. Mathematica identified seven school districts across the state to examine whether COVID-19 incidence trends for students and staff in Pennsylvania school districts using hybrid instruction paralleled or exceeded trends in the local community during the fall of 2020.