The spanking scene
Katja Hutten (Uschi Glas, aged 25) is given a classroom spanking by the entire class. They bend her over a desk and hold her in position while the other students parade in a circle around her, giving her a spank every time they pass her bottom.
The title of the film, "Klassenkeile", is a German slang term for exactly that: a spanking or beating given to a student by their classmates. Klassenkeile punishment is typically given for offenses against the whole class, or for offenses that get the whole class into trouble.
Uschi Glas is also spanked (by Roy Black) in the 1971 film Wenn mein Schätzchen auf die Pauke haut (When My Darling Stands Up).