The aim of this dissertation is to study segregation within the Swedish school system, with regard to the reformation during the last decades of the 20th century which researchers have described as a system change. After an initial research survey two questions are identified: one which concerns the process of human becoming, and the other concerning segregation, within and between social milieus in a school system. The first is answered from a relationistic philosophical perspective, which leads to the study object the educative milieu. In turn the study object leads to the development of a research approach to investigate such settings. The research approach consists in the construction of epistemic objects (in short: epiobjects) – in this case two school classes whose pupils have actively made the choice of these classes – understood as monistic entities constituted of internal relational structures. The construction of the epiobjects identifies the families involved in the classes as informants and decides on a number of research themes (for example description of the school, the teachers, leisure activities) for the data collection. The disposition of the study consists of tree main steps: determining relevant symbols, positioning and description. Determining relevant symbols means to decide what is assigned meaning in respect of the research themes. This was achieved through an interview study. Positioning means to decide how the symbols and bodies are distributed within the epiobjects in order to represent their relational structures. This was done with questionnaire data that was organised with aid of correspondence analysis. In the description the epiobjects can be understood as educative milieus, by focusing on their educative tensions and doxa. Educative tensions are differences between positions in the epiobjects relational structure, while doxa are areas of agreement. The analysis shows that the epiobjects are obviously different in terms of educative tensions and doxa. The main difference between the epiobjects concern the families’ motives for the choice they have made: families in one class maintained they chose the school because of its subject specialisation, while families in the other claimed that they sought a school characterised by orderly behaviour and a better learning of subject knowledge and skills. Associated with these differences are dissimilarities concerning, for instance, political orientation, education level, income, democracy, freedom of choice, as well as regarding inclination to attend different kinds of cultural events and institutions. The results can be seen as an illustration of how a system of freedom of choice leads to segregation, by orienting people with dissimilar preferences to different alternatives while, at the same time, these preferences concerning school choice correspond with differences in other areas of life.