Students around the world suffered historic setbacks in reading and math during the COVID-19 pandemic, with declines in test scores so widespread that the United States climbed in global rankings simply by falling behind less sharply, a new study finds.

The state of global education was given a bleak appraisal in the Program for International Student Assessment, the first study to examine the academic progress of students in dozens of countries during the pandemic. Released Tuesday, it finds the average international math score fell by the equivalent of three-quarters of a year of learning. Reading scores fell by the equivalent of half a year.

The setbacks spanned nations rich and poor, big and small, with few making progress. In the countries where students were tested, a quarter are now considered low performers in math, reading and science, meaning they struggle to perform basic math problems or interpret simple texts.