From the abstract: "BACKGROUND: In an effort to mitigate the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), North Carolina (NC) closed its K-12 public schools to in-person instruction on 03/14/2020. On 07/15/2020, NC's governor announced schools could open via remote learning or a "hybrid" model that combined in-person and remote instruction. In August 2020, 56 of 115 NC school districts joined the ABC Science Collaborative (ABCs) to implement public health measures to prevent SARS-CoV-2 transmission and share lessons learned. We describe secondary transmission of SARS-CoV-2 within participating NC school districts during the first 9 weeks of in-person instruction in the 2020-2021 academic school year. METHODS: From 08/15/2020-10/23/2020, 11 of 56 school districts participating in ABCs were open for in-person instruction for all 9 weeks of the first quarter and agreed to track incidence and secondary transmission of SARS-CoV-2. Local health department staff adjudicated secondary transmission. Superintendents met weekly with ABCs faculty to share lessons learned and develop prevention methods. RESULTS: Over 9 weeks, 11 participating school districts had more than 90,000 students and staff attend school in-person; of these, there were 773 community-acquired SARS-CoV-2 infections documented by molecular testing. Through contact tracing, NC health department staff determined an additional 32 infections were acquired within schools. No instances of child-to-adult transmission of SARS-CoV-2 were reported within schools. CONCLUSIONS: In the first 9 weeks of in-person instruction in NC schools, we found extremely limited within-school secondary transmission of SARS-CoV-2, as determined by contact tracing."