Worldwide, subject-matter teachers are commonplace in post-elementary schools. Teachers' specialisation appears as a key characteristic of secondary schools as opposed to the polyvalence of primary school teachers. Historians have already studied the long process of teachers' specialisation, which started, in France as in Prussia (for example), at the beginning of the nineteenth century and developed alongside secondary school modernisation. Those works have usually focused on professional aspects: the structuration of professional groups thanks to the unification of training and recruiting processes, the organisation of teachers within subject-matter associations etc. However, they have not paid much attention to the resistance opposed by other forms of pedagogical organisation, as if polyvalence were were just a backward anomaly, a backward anomaly, doomed to disappear. This paper seeks to shed new light on this question using a comparison between the different forms of post-elementary schooling that existed at the same time in France between the last third of the nineteenth century and the middle of the twentieth, when the slow growth of post-elementary schooling was mainly due to the success of subaltern institutions. In those institutions, dedicated to technical education, girls' secondary education, or upper-lower classes' education ("primaire supérieur", "secondaire special"), different kinds of polyvalence or bivalence were experienced in the classrooms. At the same time, specialisation was triumphing in classical secondary education. Why, how and to what extent did specialisation eventually impose itself in these different institutions? To address this question, two types of material are used. On the one hand, the question is studied on a national level, analysing both the legislation and the controversies it arouses in pedagogical and professional reviews. On the other hand, these views and theories are confronted with a prosopography of post-elementary school teachers in one department, Eure-et-Loir, which offers several forms of post-elementary institutions. This question is addressed focusing on literary disciplines (philosophy, French, Latin, Greek, modern languages and history and geography). By narrowing the scope, the intellectual and cultural stakes of the various pedagogical organisations that were implemented or advocated may more easily be grasped. The first part of the article examines the most common (though relatively untested) hypothesis: there was just one strategy for those who advocated the promotion of subaltern types of post-elementary schooling as part of a democratisation process, and this strategy was reproducing the model of the elite institution, secondary classical education, including its pedagogical organisation, starting with subject-matter teachers. The chronology of the changes, the content of the debates, as well as a comparative inquiry into teachers' remuneration induces us to discard this hypothesis as insufficient if not irrelevant. For girls' secondary education, a trade-off may be observed between equalisation (of salaries, rights etc.) and pedagogical alignment. For the other institutions, there was no lack of advocates for the specificity of the pedagogy or of the institution; however, specialisation was usually considered a process that could ameliorate the quality of teaching in these institutions without renouncing its specificity. In fact, in the period under study, the louder advocates for less specialised teachers came from secondary classical education itself: the specialisation process as well as the fragmentation of the class schedule had pedagogic inconveniences, abundantly noticed and commented on by subject-matter teachers themselves. In the second part, these critics and the two main alternatives suggested by the teachers are examined. The first is linked with the Progressive Education movement ("Education nouvelle" in French). The École des Roches, a private institution, tested an original organisation that combined the tradition of the humanities with the modern characteristic of "Éducation nouvelle": there was only one teacher for history, geography, French, Latin and Greek. The teacher was thus enabled to practise a pedagogy of interest, as advocated by Ovide Decroly. The second alternative was advocated by some modern language teachers: if modern language teachers could teach French as well as a modern language, this pedagogic organisation could give strong unity to the until then defective "modern" curriculum (without Latin). The third part turns towards the effective organisation of post-elementary schools in Eure-et-Loir. To what extent were these alternative conceptions of pedagogical organisation implemented? The analysis of individual records of teachers suggests several results. First of all, in small institutions – be they classical secondary institutions like "collèges" or modern ones like "écoles primaires supérieures" – specialisation of services was a luxury that most teachers could not afford. Most of the time, they had to teach several subjects, even if they had been trained for just one. However, polyvalence was not used as an opportunity to make connections between the subjects. Class schedules rarely enabled teachers to use polyvalence as a way to teach several subjects to the same pupils. More often, polyvalence was used by the administration as an expedient that some teachers explicitly tried to escape, for example by asking for a move to a bigger institution. This mundane reality of small institutions invites us to pay renewed attention to teacher training and its regulation during the same period. At the end of the nineteenth century, teachers' specialisation had been inextricably linked with the modernisation of universities through the specialisation of the "licence de lettres" in 1880. When this model proved to be partially irrelevant for a significant proportion of post-elementary schools, how did universities react? Were universities fit for something other than training specialised teachers? The answer is yes. The curriculum organisation of the licence opened up several possibilities for training polyvalent teachers. This perspective was still looming at the end of the 1930s. The curricula of the different post-elementary settings analysed in this article shared the same characteristics: they worked as "serial codes" not as "integrated codes", to quote Basil Bernstein. Therefore the specialisation, bivalence or polyvalence of the teachers did not have much influence, in itself, on the degree of integration of the curriculum. From this perspective, specialisation could probably guarantee better teaching of the subject matters. However, polyvalent teachers were better suited to small schools than specialist ones. Considering demographic and geographic constraints, there was a clear trade-off between specialisation of teachers and separation of publics. In small cities, it was necessary either to mix the pupils to specialise the teachers, or to accept some kind of polyvalence to keep different types of students separated; the debate was still open during the 1930s. School massification, coeducation and the baby-boom era rapidly settled the matter for small cities after the Second World War, giving way to an effective specialisation of teachers. But the question remained open, until the end of the 1970s, for rural settings. [ABSTRACT FROM AUTHOR]