In this case study, we describe and document how Baltimore City Public Schools (BCPS), an urban K–12 public school system, implemented COVID-19 mitigation measures guided by a Public Health Advisory Committee, as well federal and state guidance. BCPS comprises more than 160 public schools, and offers education and social safety services to a population of almost 76,000 students. Throughout the 2020–2023 academic years, BCPS worked with a Public Health Advisory Committee to establish comprehensive COVID-19 transmission mitigation measures, using federal and state pandemic-related funding meant to reduce COVID-19 prevalence among students, faculty, and staff. The school system’s processes of determining and establishing these mitigation measures over the three academic years provides valuable information and lessons for preparing schools in the event of future health emergencies or pandemics, particularly related to decision-making processes, and student/parent communications.