Starting in the 3rd century AD, unfavorable climatic changes and overpopulation led peoples from Eastern Europe and Asia to set out in increasing numbers on a search for a new home. Marcomanni, Goths and Huns penetrated the Roman borders time and again and occupied our land, often for years at a time. The Great Migrations had begun. In 486 the Romans finally gave up and withdrew to Italy. The Langobardi, the Avars and above all the Slavs soon made deep incursions into this no man's land. Leesdorf, for example, was founded by a Slavic leader named Lev. Starting in 796 Charlemagne began conquering what is today eastern Austria and incorporating it into the Frankish Empire. His great-grandson Carloman, who later became emperor himself, established a palatinate in Baden. The Carolingian Empire had no capital city. Instead the rulers traveled throughout the realm and saw to it personally that peace and order were preserved.

It was for this purpose that palatinates were set up where an administrator amassed supplies all year long so he would be able to feed the ruler and his retinue for the few weeks they were in Baden. We know from a document that Carloman held court in 869 in the Palatinate of Padun. Padun is the Old High German form of the town's present name Baden. The naming of Padun is important for all of Austria, because the next palatinates were Karnburg (today the Austrian province of Carinithia) and Enns (on the border between the present-day provinces of Lower Austria and Upper Austria).
Over the centuries, the main structuring of the Baden palatinate developed into the Baden fortress located at the present-day site of the parish school.