text: The effects of school closures on SARS CoV 2 among parents and teachers To reduce the transmission of severe acute respiratory syndrome coronavirus 2 SARS CoV 2 most countries closed schools despite uncertainty if school closures are an effective containment measure At the onset of the pandemic Swedish upper secondary schools moved to online instruction while lower secondary schools remained open This allows for a comparison of parents and teachers differently exposed to open and closed schools but otherwise facing similar conditions Leveraging rich Swedish register data we connect all students and teachers in Sweden to their families and study the impact of moving to online instruction on the incidence of SARS CoV 2 and COVID 19 We find that among parents exposure to open rather than closed schools resulted in a small increase in PCR confirmed infections odds ratio OR 1 17 95 CI CI95 1 03 to 1 32 Among lower secondary teachers the infection rate doubled relative to upper secondary teachers OR 2 01 CI95 1 52 to 2 67 This spilled over to the partners of lower secondary teachers who had a higher infection rate than their upper secondary counterparts OR 1 29 CI95 1 00 to 1 67 When analyzing COVID 19 diagnoses from healthcare visits and the incidence of severe health outcomes results are similar for teachers but weaker for parents and teachers partners The results for parents indicate that keeping lower secondary schools open had minor consequences for the overall transmission of SARS CoV 2 in society The results for teachers suggest that measures to protect teachers could be considered 