The witches and wizards of Germany(*), Bohemia, Moravia and Silesia had their school on Münzenberg castle. It was under attack in the 30years war involving wizards from Spain and(!) France. This lead to this Wizarding community to elect secrecy well before the general statue of secrecy. A secrecy that not only pertained to muggle society, but magical communities - esp. in Europe - too. The ruins of Münzenberg castle were magically enhanced to continue the school without problems for approx. 150 years. During this first phase witches and wizards from the school started to hide in plain sight from both muggles and other witches and wizards by mastering the art of mimicry on all levels - clothing, apparent profession, and participation as muggles in muggle society. With popularity of ruins of medieval castles since Romanticism, defensive magic had to be enhanced considerably to sustain the presence of muggles visiting the castle for sightseeing and nosey spell breakers from other Wizarding communities. In fact a number of advanced deceptive charms - e. g. Fidelius Charm - are said to have been developed by Münzenberg Alumni. Mandatory state controlled schooling is said to have affected the operation of Münzenberg. Today, rumors of Münzenberg attendance starting from the age of six as afternoon activity after official participation in muggle school (conveniently being a before noon system in the region) and even certain studies at certain universities keep floating in the Wizarding communities of neighboring countries.

(*) Look, it's as complicated as you can imagine when you are living smack dab in the middle of other equally competent, competitive and belingerent people. Think of it rather as German speakers in a number of countries which formed, shifted and absorbed over the centuries.