School segregation remains a significant educational and social challenge across many educational systems. In Europe, this issue has gained policy relevance in the past decade, particularly in educational quasi-market contexts (Dupriez et al., 2023; D’Agostino, 2024), where the role that choice and school competition play in contributing to segregation has been particularly scrutinised. In response to the increasing problematisation of school segregation, authorities have adopted policy initiatives to regulate school choice, school admissions or public subsidies for private schools, with the objective of reducing school segregation. However, the evidence about the capacity of these policies to address segregation dynamics remains inconclusive. In the few contexts where desegregation policies have been evaluated, results show null or moderate effects in achieving a more even distribution of students (see, for instance, Danhier & Friant, 2019; Grenet et al., 2023; Honey & Carrasco, 2023). In 2019, Barcelona’s Local Education Authority adopted the Shock Plan Against School Segregation (SP), a pioneering initiative within the Spanish context, to promote a more balanced distribution of disadvantaged students among the city's schools. The SP aims to achieve this objective through three policy instruments: targeted funding, preassigned school seats and quotas for low-income students. Barcelona represents a particularly relevant case for analysing the effectiveness of desegregation policies in quasi-market settings, given its high proportion of private subsidised school enrolment and the wide range of school choice options available to families—features identified as key drivers of school segregation in the city (Bonal et al., 2021). This paper aims to analyse the impact of the SP on the school segregation of low-income students. Using a quasi-experimental approach based on an Interrupted Time Series design (Kontopantelis et al., 2015), the study estimates the SP’s impact on the distribution of disadvantaged students across schools, their concentration, and stratification between public and private subsidised schools. The findings demonstrate that the SP has effectively reduced school segregation in aggregate terms. Nevertheless, the analysis reveals heterogeneous policy impacts according to the educational, socioeconomic, and urban characteristics of the different catchment areas. These findings demonstrate that the effectiveness of desegregation policies varies depending on the specificities of the local education markets in which they are implemented. The paper concludes by elaborating on the opportunities, limits and challenges of desegregation policies in quasi-market contexts to favour a more balanced distribution of students, as well as to compensate for the tendency of market-oriented policies to exacerbate segregation dynamics.

Bonal, X., Zancajo, A., & Scandurra, R. (2021). Student mobility and school segregation in an (un) controlled choice system: A counterfactual approach. British Educational Research Journal, 47(1), 42-64. D’Agostino, T.J, Vernimmen, J., & Feldman, A. (2024). Reforming school choice systems to reduce segregation in schools: A comparative political economy study of education reform in Belgium, Chile, and the Netherlands. Peabody Journal of Education, 99(5), 596-620. Danhier, J., & Friant, N. (2019). Assessing local socioeconomic desegregation: The effects of successive decrees regulating school choice in the Belgian French-speaking community. European Educational Research Journal, 18(2), 248–268. Dupriez, V, Valenzuela, J.P, Verhoeven, M. & Corvalán, J. (2023). Educational Markets and Segregation Global Trends and Singular Experiences from Belgium and Chile. Springer. Grenet, J., Huillery, E., & Souidi, Y. (2023). Mixité sociale au collège: premiers résultats des experimentations menées en France (Note du CSEN, 9). CSEN. Honey, N., & Carrasco, A. (2023). A new admission system in Chile and its foreseen moderate impact on access for low-income students. Educational Evaluation and Policy Analysis, 45(1), 108-133. Kontopantelis, E., Doran, T., Springate, D.A., Buchan, I., & Reeves, D. (2015). Regression based quasi-experimental approach when randomisation is not an option: interrupted time series analysis. bmj, 350.