Intensive "German as a foreign language" (DaZ) courses are the standard priority.
Many students are placed in separate, preparatory classes to focus almost exclusively on learning the German language before moving into standard subjects. 2022---What-refugee-children-can-expect-at-German-schools
Because education is managed by 16 individual federal states rather than a single national authority, the "first day" experience varies significantly depending on where you live. Intensive "German as a foreign language" (DaZ) courses