With the onset of the coronavirus disease 2019 (COVID-19) pandemic in February 2020, the majority of European countries experienced 2 national lockdowns, which involved school closing, imposed by governments to control spread of the virus. In September 2020, on the reopening of the schools after the first lockdown, serious concerns were raised in Europe by scientific societies and governments on the possible role of schools in facilitating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) circulation in the population. In response, European countries produced technical documents and guidelines on COVID-19, which included guidance for a safe reopening of schools and children's educational services. Different preventive strategies were adopted by European governments to control suspected and confirmed cases of infection in the school environment.1 ,2 In February 2021, based on available epidemiologic data, public authorities in Europe considered establishment of a third general lockdown of the population, as a preventive measure to combat a resurgence of the infection, mainly caused by variants of the original virus.3 An extended school closing was also considered by many European countries as a part of their third lockdown strategy.