This article shows how the Catalan government has not developed an agenda to tackle school segregation despite the growing number of migrant pupils who arrived over the course of the last decade. Education policy has explicitly disregarded the possibilities of improving the regulatory framework for tackling segregation; it has exercised insufficient control over the effective application of education regulations on the balanced schooling of pupils with specific educational needs; and it has taken decisions on education policy which have even accentuated school segregation. This article provides empirical evidence on the characteristics of school segregation in Catalonia and on the education policies developed by the Catalan government in the domain of the schooling of migrant pupils. The study illustrates how the absence of an explicit school desegregation policy is an example of the politics of non-decision-making and a case which clearly manifests the need to overcome behavioural analysis in policy decision-making.