Conversation so far:
Who is Busoni in relation to Kurt Weill?
After examining some of Kurt Weill's compositions, Busoni accepted him as one of five master students in composition at the Preußische Akademie der Künste in Berlin.
When was that when Busoni accepted Kurt Weill as one of five master students in composition at the Preußische Akademie der Künste in Berlin?
Kurt Weill had an interview with Ferruccio Busoni in December 1920.
Were the other master students in composition at the Preußische Akademie der Künste in Berlin with Kurt Weill well-known?
What did Busoni think of Kurt Weill's compositions?

Question: How long did Weill continue to study with Busoni?
Self-contained rewrite: How long did Weill continue to study with Busoni?