Researchers from Innovamat Research Lab and EsadeEcPol claim the OECD altered its methodology for measuring socioeconomic levels in the PISA report. The study suggests that variables from 2022 and 2025 were compared despite being technically incomparable.
The 2025 index removed 11 indicators, including questions about books, adding items like swimming pools and security systems. While the PISA Technical Report warned against comparisons, Volume I compared these statistics against previous cycles regardless.
Recalibrated data shows the performance gap in Mathematics between socioeconomic quartiles changed by only 1.6 points, not the 11.2 points reported. Experts confirm the global decline is real but occurred equally across all student socioeconomic groups.