What is PISA, and why will Catalonia lack comparable results?

PISA is the world’s largest international assessment of education, organized by the OECD and involving 91 countries. Its results will be released on Tuesday, Sept. 8, including Spain’s performance.

The assessment examines what 15-year-olds know and can do with what they have learned at the end of compulsory secondary education. It measures skills rather than memorized content. Researchers test a representative sample rather than every student, using factors such as gender, socioeconomic background and school type to construct it.

About 40,000 students from 1,000 schools took part in Spain. The country’s autonomous communities funded expanded samples so analysts could produce statistically valid results for each territory as if they were separate countries. Catalonia, however, will not have a representative sample in this edition because of a sampling error.

PISA results use a scale centered on 500 points. In 2022, Spain scored 472 in mathematics, 476 in reading and 485 in science. Performance levels run from 1 to 6, allowing countries to see how many students reach the highest levels or remain among the lowest performers.

The core subjects are mathematics, reading and science, with one receiving deeper attention in each cycle. Science received the strongest focus in PISA 2025. The assessment also examines an additional skill in each cycle. This edition includes students’ ability to solve problems through the digital world, while results for that area and English as a foreign language will come next spring. Spain’s results, which usually fall below the OECD average, influence the political agenda and education reforms.