A critical sampling error in Catalonia’s 2025 PISA assessment has triggered political and institutional fallout, leaving the region unable to compare its educational outcomes with those of other territories. Catalonia was excluded from the OECD’s international report after the sample-selection failure, depriving policymakers and researchers of comparable results for the 2025 cycle. PISA assesses 15-year-old students’ skills in reading and mathematics, with science as another basic area. Its comparisons depend on samples that represent the populations being assessed.
Esther Niubó, Catalonia’s education minister, faced questions from parliamentary groups after her explanations failed to clarify how the error went undetected for months. The issue became public after four months of silence, fueling frustration among opposition parties and coalition partners ERC and Comuns. A special parliamentary session requested by Junts per Catalunya was ultimately dropped, while President Salvador Illa was expected to address the matter after the summer recess.
At the centre of the controversy is the finding that 23.2% of students who should have participated in the PISA assessment were declared exempt, compared with the OECD’s stated 5% threshold. The anomaly affected 51 randomly selected schools between March and May 2025. The OECD notified Catalan authorities in March, prompting an internal investigation that remains open. Catalan reporting has also raised questions about why seven warnings reportedly sent by Spain’s Ministry of Education were not acted upon. Niubó has argued that disclosing details could compromise the inquiry, while opposition parties have accused the department of lacking urgency and clarity.
The sampling failure has consequences beyond the disputed administration of the test: without a valid, representative sample, Catalonia cannot use its 2025 results to benchmark student performance against Spain, other autonomous communities or international participants. Niubó has said the full impact on the region’s ability to compare results with previous years became clear only later. The exclusion means no Catalonia-specific 2025 result can serve as a comparable score in the OECD dataset.
Although the root cause has not been identified, the Education Department has introduced clearer protocols for evaluation processes and centralized validation of student exemptions, as well as a new Commission for Coordination of Tests and Evaluation Studies. The commission overlaps with the Agency for Evaluation and Foresight, which began operating in July 2025 after years of inactivity and was intended to simplify educational assessments. The reorganization has raised further questions about how the department divides responsibility for testing and oversight.
The timing of the public announcement has also drawn criticism. The government had known about the issue since March but did not disclose it until the end of the academic year, a period already marked by labor disputes and strikes in education. Niubó, who was on medical leave for two months because of cancer, did not specify who decided to delay the announcement. The Education Department says it investigated before going public; opposition parties have called the delay an attempt to avoid accountability. The dispute has also fed a wider debate in Catalonia about inclusive schooling and teacher professionalism, alongside questions about shared responsibility between schools and families.
Questions have focused on who made basic decisions during Niubó’s absence. Her deputy, Teresa Sambola, led the department, while Presidency Minister Albert Dalmau handled institutional representation. Opposition parties have pressed for details about when Illa was informed. By October 2026, the controversy was still being discussed as an unresolved institutional crisis. VilaWeb reported that Niubó had dismissed former secretary-general Teresa Sambola and that the government was seeking to reassign her. Information from VilaWeb, the government said the personnel change was not directly because of the scandal, though the controversy had been the final trigger. The dismissal was not presented as a formal disciplinary finding.
The episode has become part of broader scrutiny of Spain’s education system, including concerns about regional disparities and governance. The PISA failure has intensified questions about administrative accountability and communication inside Catalonia’s Education Department. The wider debate has included calls for practical measures to address dissatisfaction with the system, rather than treating the sampling error as an isolated statistical problem.
PISA is an international assessment used to compare education systems, and its findings inform policy discussions and research. Spain has participated since the programme began. Catalonia’s exclusion from the 2025 report removes a basic comparative measure for the region’s education planning and complicates national and international assessments. Unresolved questions about the sample and reported ministry warnings, along with the handling of the disclosure, have made oversight and clear lines of responsibility basic issues in the continuing debate.
