Lehrplan; Syllabus; Curriculum research ; 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) ; Lehrerausbildung; Teacher training; Lehrerfortbildung; In-service teacher training; Teacher education ; Second language acquisition in children; Kindlicher Zweitspracherwerb; Child second language acquisition