Question:
Where was Walter Ledermann educated in Nov, 1919?

Context:
 Walter Ledermann attended University of St Andrews from Jan, 1934 to Jan, 1936. 
 Walter Ledermann attended Frederick William University from Jan, 1928 to Jan, 1933. 
 Walter Ledermann attended Köllnisches Gymnasium from Jan, 1917 to Jan, 1920.

Answer:
Köllnisches Gymnasium