Throughout the political upheavals that had an impact on the European continent over the last three decades of the Eighteenth century, the missions, contents, methods and organization of the educational world were profoundly remodeled. Mainly restricted to an elite and focused on the humanities, education diversified and democratized itself and gradually became a public matter and a State concern which reformed its educational system and integrated a larger part of its population into the public and political sphere. On the eve of the Nineteenth century, the secondary education developed and changed under the action of governments, but also and especially thanks to the commitment of schoolmen. A case study devoted to the work of a Berliner pedagogue and man of the Enlightenment, Friedrich Gedike (1754-1803), and to the two secondary establishments he successively directed between 1779 and 1803, allows not only to extend and deepen knowledge of the Prussian educational landscape and the Berliner Enlightenment, but it is also exemplary on more than one account. It illustrates the creative initiative of schoolmen engaged in a profound reform of education and the Prussian society of the last two decades of the century. Moreover, it highlights the metamorphose of secondary-level education which stands out from universities and diversifies itself with inferior classes proposing a more practical teaching (Bürgerschule) and superior classes preparing for university while teaching humanities (gelehrte Schule). Progressively, the curricula of secondary schools began to propose a balance between linguistic and scientific teaching, but also between ancient and modern languages. The student population began to change: diversifying and democratizing itself. Merit imposed itself little by little as a form of selection and access criteria to higher education and power. Finally, this case study shows the politicization of educational debates and reforms. Through a reform of education, schoolmen and men of letters aimed at a deep reform of society: creating the conditions for tolerance, a real “living together” between social orders, confessions, corporations, and to a certain extent genders, replacing privilege of birth and wealth by individual merit. Moreover, secondary schools became places of learning about a vibrant political culture. Humanities training was accompanied by a citizenship training with an opening up to the modern world, to immediate history and to national and foreign policies. Intellectual curiosity, personal thought, critical thinking and a debating culture were encouraged daily among students. Prussian High Schools became a privileged place for the constitution of a public sphere that would dialog with the institutional power or get access to it, allowing the integration of a larger and diversified part of the population to take part in political decisions. This study demonstrates the importance and the singularity of Friedrich Gedike in the history of education in Prussia.