DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; Fremdsprachenunterricht (Grundschule) ; Foreign language teaching (elementary school) ; Modern Languages at Primary School; Kindergarten (Fremdsprachenunterricht) ; Kindergarten (foreign language teaching) ; Vorschule (Fremdsprachenunterricht) ; Nursery school (foreign language teaching) ; Preschool (foreign language teaching) ; Elementary school (foreign language teaching) ; Gastarbeiterkinder; Migrant workers (children of) ; Auswanderer (Kinder) ; Emigrants' children; Migrantenkinder; Aussiedler (Kinder) ; Kinder mit Migrationshintergrund; Immigrants'/Emigrants' children ; German