The 2013 edition of the survey was a wake-up call for Sweden, which experienced a sharp drop in the results of 15-year-old students, pushing them below the OECD average and sparking debate about the country’s schools.

But Tuesday’s release of the 2018 Pisa ranking suggests that Swedish schools have further improved on a recovery that started with the 2016 edition, with above-average scores in reading, mathematics and science.

The report notes that Sweden is back at levels observed in early rankings, despite a rapid increase in the proportion of immigrant students, who tend to score below native-born students, in recent years. In 2018 around 20 percent of students in Sweden had an immigrant background, up from 12 percent in 2009.