DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; Lehrplan; Instructional advice ; Classroom communication; Instructional communication ; Gastarbeiterkinder; Migrant workers (children of) ; Auswanderer (Kinder) ; Emigrants' children; Migrantenkinder; Aussiedler (Kinder) ; Kinder mit Migrationshintergrund; Immigrants'/Emigrants' children ; Case study (second language acquisition) ; German