REICE. Revista Iberoamericana sobre Calidad, Eficacia y Cambio en Educación

School segregation by socioeconomic characteristics in secondary education in the Autonomous Community of Madrid is the highest in Spain and second highest amongst OECD countries. This study aims to analyze the influence of the implementation of the bilingual program in Madrid from the 2004/05 academic year on school segregation, and its consequences on student performance. The findings indicate that families in non-bilingual schools have a lower socioeconomic level than families in bilingual schools. School segregation gradually increased between 2009 and 2018 for two reasons: the expansion of publicly funded private schools over the previous decade and the expansion of the bilingual program. In 2015, when the bilingual program reached the last course of secondary education in public schools, school segregation notably increased within the public system. Likewise, in 2018 school segregation notably increased within publicly funded private schools, consistent with the arrival of the bilingual program in the publicly funded private sector at the end of secondary education. Finally, we observe that students from non-bilingual schools underperformed students from bilingual schools on the PISA tests.