Student reduction is not common practice everywhere in Saarbrücken, but some baths, cinemas, museums etc. offer it. Ask for "Studentenermäßigung". Be prepared to show your student identity card / Semesterticket.
Some places that offer student reduction: Filmhaus cinema, Cinestar cinema, Staatstheater, Volkshochschule / adult education centre (not on all courses), Zoo Saarbrücken, Zoo Neunkirchen, Stadtbibliothek.