Once the models for the selection of schools with high and low effectiveness were applied, their identification was carried out. First of all, an analysis of the selected schools by autonomous region can be carried out, with the following chart showing the results.

Source: Adapted from Gamazo, Martínez-Abad, Olmos-Migueláñez & Rodríguez Conde (2018)

It is observed that certain autonomous regions have a clearly higher proportion of schools with high effectiveness (high residual) in relation to the selection of schools with low effectiveness, such as La Rioja, Navarra, Murcia, Madrid, Aragon and, especially, Castile and León. In the case of selected schools with low effectiveness (low residual), we find several regions that make important contributions: Asturias, Canary Islands, Extremadura, Andalusia and, especially, the Basque Country.

The case of the Basque Country is worthy of more in-depth study since, despite it being an autonomous region with one of the highest socio-economic levels in Spain, most of the schools selected were determined to have low effectiveness. This autonomous region’s own linguistic educational models and the language in which the PISA performance tests were carried out may have had a spurious effect on these results.