The title echoes the well-known phrase "the idea of the university", and European universities have always been seen as institutions with a strong international dimension, developing according to common patterns. In their case, it was the "Humboldtian" model embodied in the University of Berlin founded in 1810 which prevailed. For secondary schools, the lycees of Napoleon and the German Gymnasien, both taking shape around 1800, share this role. The main features of the lycee/Gymnasium model can be summarized: they were public, secular institutions; they were part of an elite sector with little organic connection with popular education; they were oriented to preparing for higher education, with a predominantly classical curriculum, taught by specialist teachers trained in the universities; and they offered an eight or nine year course culminating in an examination (baccalaureat, Abitur) which came to define a completed secondary education. Some of these features came from the common European heritage of humanist education, others were due to political and social developments in which all European countries shared-secularization, the growth of the middle class, the impact of the French revolution, etc. But there could be crucial national differences in the timing of such developments, and in the degree to which the values of old and new elites were fused together. One argument of this paper is that the new model long remained an "idea" or conceptual framework rather than a reality, even in its French and German homelands, and that the uniform concept concealed many historical variations. And after around 1870, new moulding forces took over (industrialization, mass politics, nationalism), though these too gave a strong impulse to uniformity. The new relationship between secondary schools and universities did not become definitive in many countries until quite late in the 19th century. The word "secondary" could be used in different senses, and boundaries cold shift. On the one hand, traditional universities had included forms of preparatory general education which the new model defined as secondary and pushed back into the schools. On the other, as in the Bavarian or Austrian Lyzeum, the Dutch "illustrious schools", or the English Dissenting Academies, intermediate institutions had developed which straddled secondary and higher education. Assimilation to the new pattern usually accompanied adoption of the "Humboldtian" university ideal, and took place mostly between 1848 and the 1870s, though sometimes as late as the 1890s. The acceptance of 18/19 as a "natural" age of transition itself needs explaining, and is clearly connected with the history of adolescence The existence of a network of secondary schools, often as part of state structures which included precise legal definitions of their function, could conceal huge variations in the real role of schools in their local context. Even in a highly centralized system like the French one, historians are discovering the significance of local initiative and adaptation to local needs. In Germany, recent research has shown quite strikingly that the Gymnasien of the early 19th century were both multi-functional in their curricula, and diverse in their social recruitment. Educating the elite, and giving an intensive humanist education, were only part of the functions of such schools. Historical generalizations have tended to overlook both the mass of pupils who left them at an early stage, and the diversity of the school pattern itself (religious schools in France, modern schools in Germany, private schools in Britain, etc.). Religious, ethnic and linguistic divisions could overlay those of social class. We should also recall that secondary schooling was a market, in which state policy had to compromise with parental preferences and family strategies. Studies of secondary schooling within its urban social and cultural context are one of the most potentially fruitful lines of current research In the later 19th century, the multi-functional role of schools diminished as industrialisation both expanded and differentiated the demand for schooling, a process studied by Fritz Ringer and others. It is in this context, perhaps, that the creation of modern forms of secondary schooling for girls is best seen. Within a new variety of "tracks", the humanist secondary school became a specialized and more privileged type, fiercely defended by academic conservatives. Yet there remained close parallels between the various European systems: developments followed much the same chronology, and models such as the German Realschule were closely studied; even Britain was conforming to "continental" patterns by the 1900s. In the age of the nationstate, great-power rivalry, mass politics, and universal literacy, the training of a homogeneous national elite, an "intellectual aristocracy" to provide stable leadership, became a general preoccupation. Just as this was true of the major powers, so the formation of such an elite through education was crucial to the demands of ethnic minorities now seeking emancipation within the multi-national empires, as well as linguistic ones within some unitary states. In recent years, theorists of nationalism have emphasized the importance of education for the emergence of the modern nationstate, and conversely historians of education must see nationalism as a powerful shaping force. This represents one of the ways in which, as in other fields of historical scholarship, interest has swung from the social themes which dominated research in the 1960s and 1970s to cultural and political ones.