Catalonia's PISA 2025 sample invalid after 23% of students excluded, ombudsman opens probe

Catalonia's results in the 2025 PISA assessment will not be comparable with previous editions or other regions after 23.2% of the selected students were excluded from the tests, far exceeding the 5% maximum set by the OECD. The Catalan ombudsman has opened an investigation, and President Salvador Illa is set to address the controversy today.

The exclusion error

The PISA 2025 sample in Catalonia comprised 2,545 students aged 15 to 16, drawn from 51 schools. Of these, 591 were exempted, pushing the exclusion rate to 23.2%. The OECD's technical standards cap voluntary exclusions at 5% to preserve statistical validity. The bulk of the exemptions, 19.6% of the total sample (499 students), were justified on grounds of cognitive, emotional, or behavioural disabilities. A smaller number were excluded for physical disabilities or insufficient knowledge of the test language, which in Catalonia is exclusively Catalan.

Voluntary exclusions must not exceed 5%, and Catalonia has far exceeded that. Countries that go over get an asterisk so their results are treated with caution. Usually the excess is between 6% and 8%, but the Catalan case has gone off the rails.

The error was not confined to a handful of schools. Each centre can contribute a maximum of 42 students, so a deviation of this size points to a systematic problem across many of the 51 participating centres. The tests were administered between 31 March and 16 May 2026. Catalonia will still appear in Spain's national report when the OECD publishes its findings on 8 September, but its data will carry a methodological warning and cannot be used for reliable comparisons.

Ombudsman investigation

On 30 July, the Síndica de Greuges (Catalan ombudsman) Esther Giménez-Salinas opened an official inquiry. She has asked the regional education department for detailed information on the 51 schools in the sample, the characteristics of the excluded students, the supervision mechanisms applied during the test period, and a copy of the internal report being prepared by the department's own fact-finding inquiry.

Giménez-Salinas highlighted the disproportionate share of exclusions attributed to disabilities. The 19.6% figure, she noted, is far above the prevalence of students with special educational needs in the fourth year of compulsory secondary education, which stands at around 5%. She also contrasted the PISA exclusion rate with the 9.7% exemption rate recorded in Catalonia's own basic skills tests for the same cohort, a discrepancy that deepens concerns about the criteria applied.

PISA tests are a reference tool for evaluating the functioning of education systems and guiding public policies. It is essential to clarify how this incident occurred.

Political pressure

The affair has placed Education Minister Esther Niubó under intense scrutiny. Opposition parties Junts, the People's Party, and Vox have demanded her resignation. President Illa has so far backed his minister, describing the episode as a technical failure. He is expected to give a public account of the events today, though a full explanation may not emerge until after the OECD releases its global results in September.

What comes next

Catalonia will have to wait until the next PISA cycle, scheduled for 2029, to obtain comparable international data on its education system. The region had been hoping to check whether it had reversed the sharp decline recorded in the 2022 edition. The ombudsman's investigation will run in parallel with the education department's internal review. For now, Catalonia loses the benchmark it had sought.