This happened everywhere, including in the places that only shut down in-person schooling for March 2020-May 2020, and opened up again in August 2020.
Maybe the effect of going through a pandemic was a stressful event harmful to school performance, independent of whether your schooling was in-person or remote?
>Education ministries the world over will envy the handful of rich places that have a cheery story to tell amid the gloom. In Japan, Singapore, South Korea and Taiwan, test scores not only held steady over the pandemic period, they actually ticked up in at least one of the three subjects in which pupils sat exams. Israel and Switzerland are among other countries that appear, at least as judged from these data, to have done reasonably well.
>Some of these outliers protected learning by keeping school closures short. Across the OECD’s dataset there is a modest association between the length of time schools stayed closed and children’s subsequent performance in tests. Teachers in Switzerland ran fully remote or hybrid timetables for only six weeks (the average among countries in Europe was around 29). Closures in Japan were also comparatively zippy: in 2020 schools in that country shortened their summer breaks in order to claw back some of the class hours that children had lost up to then. Singapore, likewise, decided to alter school holidays to maximise learning time.
Maybe the effect of going through a pandemic was a stressful event harmful to school performance, independent of whether your schooling was in-person or remote?