Question: What school of composers was attended by the composer whose operas were considered the only German ones more important than "Die Soldaten" by Bernd Alois Zimmermann?
Sentence (from "Bernd Alois Zimmermann"): He is perhaps best known for his opera "Die Soldaten", which is regarded as one of the most important German operas of the 20th century, after those of Berg.
Relevant evidence: Yes