Guide for teachers in secondary education at secondary schools, comprehensive schools, and grammar schools. Elif looks at you questioningly during physics class - she struggles even with simple textbook texts. Dimitri knows everything about the Middle Ages - but during his presentation, no one understands what it's about. Two typical situations from different subjects in a class with students from migrant backgrounds or German as a second language (DaZ): they often do not understand subject texts and terminology and cannot adequately articulate their existing knowledge. As a result, they often reach their linguistic limits and ultimately lose motivation. This manual explains how to prevent young people from failing due to insufficient German language skills. An overview of the most common language problems shows where you should focus your attention. It is followed by tips for diagnosing language abilities.