This paper presents the results obtained in the second stage of national RTD project MIXSTRIN: Ways of grouping students together and how this is related to success at school: Mixture, Streaming and Inclusion. The main objective of this research is to provide evidence of how students are grouped in primary and secondary schools in Spain, and how the different grouping options contribute either to school success or to school failure. In the first stage of the research, a quantitative study was conducted surveying a representative sample of primary and secondary public schools in Spain. It allowed us to establish the incidence of three different forms of grouping students; mixture –traditional classrooms with diverse students and only one teacher–, streaming –classroom arrangements that group students homogeneously and adapt teaching to their level ofattainment, often including additional teachers–, and inclusion –which entails reorganising human resources to support all students in heterogeneous classrooms.

The limitations of mixture classes to respond to a group of diverse students have not been addressed successfully by streaming practices. Diverse studies in the last decades have provided evidence on this (Braddock & Slavin, 1992; Chorzempa & Graham, 2006; Zimmer, 2003). However, streaming actions are still being put into practice in many schools across Europe, and in Spain have even been included in education laws. Cooperative learning (Braddock & Slavin, 1992; Johnson, Johnson, & Holubec, 1994; Slavin, 1991; Stevens & Slavin, 1995) is an alternative to ability grouping that has demonstrated to promote positive effects on learning, self steem, acceptation of students with disabilities and intercultural relationships. Establishing help interactions between students with different levels of attainment in order to achieve shared aims is one main characteristic. The dialogic learning is also based on cooperation between students but goes one step beyond as it promotes learning through dialogue not only aming students but with all the educational agents that interact with them (Aubert, et al. 2008, Elboj, et al. 2002; Flecha, 1997; Freire, 1998; Wells, 1999).

The second stage of MIXSTRIN deepen from a qualitative approach on the way that the two main forms of grouping which are alternatives to mixture–streaming and inclusion– influence the educational outcomes of students, in the context of Spain. With this aim, a qualitative study in five Spanish schools was carried out, including primary and secondary schools, which represent both modalities of grouping. This has allowed understanding which way of grouping students respond better to the diverse needs of the student body and help all of them progress in their learning and achieve successful educational outcomes. This analysis starts from the definition of school success that takes into account both academic performance of students, including the dimensions of excellence and equity, and non-academic results such as absenteeism reduction, enrolment increases, or the improvement of the coexistence. The results of this research allow us to draw conclusions that will guide both practical proposals to develop in schools as policy recommendations.

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