More than a third of the U.K.’s 1,700 coronavirus outbreaks, defined as at least two cases, in the four weeks through Sept. 27 occurred in educational settings. About 35% of the 1,070 outbreaks under investigation in France are in schools or universities. Spain, home to Europe’s biggest epidemic, reported Covid-19 cases in 4.5% of its schools as of Sept 24.

In Italy, where the virus’ resurgence has been much slower, the government reported 2,438 cases among elementary, junior-high and high-school students as of Oct. 3, compared with 809 two weeks earlier. Germany hasn’t reported national data showing the impact of the virus on its school system, but public-health authorities said this week it appeared that the pandemic hasn’t had a great impact on schools since they reopened.

Authorities have responded to some of the outbreaks by quarantining classes or, on rare occasions, shutting down entire schools. In most cases, however, European officials and many parents have pushed their schools to remain in session, saying the social and economic cost of missing school is too high.