Among tool kits to combat the coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, school closures are one of the most frequent non-pharmaceutical interventions. However, school closures bring about substantial costs, such as learning loss. To date, studies have not reached a consensus about the effectiveness of these policies at mitigating community transmission, partly because they lack rigorous causal inference. Here we assess the causal effect of school closures in Japan on reducing the spread of COVID-19 in spring 2020. By matching each municipality with open schools to a municipality with closed schools that is the most similar in terms of potential confounders, we can estimate how many cases the municipality with open schools would have had if it had closed its schools. We do not find any evidence that school closures in Japan reduced the spread of COVID-19. Our null results suggest that policies on school closures should be reexamined given the potential negative consequences for children and parents.

在对抗由严重急性呼吸综合征冠状病毒 2 引起的 2019 年冠状病毒病 (COVID-19) 的工具包中，关闭学校是最常见的非药物干预措施之一。然而，学校停课会带来巨大的成本，例如学习损失。迄今为止，研究尚未就这些政策在减轻社区传播方面的有效性达成共识，部分原因是它们缺乏严格的因果推断。在这里，我们评估了 2020 年春季日本停课对减少 COVID-19 传播的因果影响。通过将每个拥有开放学校的城市与一个在潜在混杂因素方面最相似的拥有封闭学校的城市进行匹配，我们可以估计如果关闭学校，拥有开放学校的市政府将会有多少病例。我们没有发现任何证据表明日本关闭学校可以减少 COVID-19 的传播。我们的无效结果表明，考虑到对儿童和家长的潜在负面影响，应该重新审查关闭学校的政策。