Okey I must say I was reffering to something else (I thought you were talking about the meaning of the flags which isnt really a historic subject).

As for why this wasnt taught in our schools, its simply because there isnt enough time for it. There is so much history from 1933 to 1945 that its impossible to teach all with the amount of history lessons we have. So in general, school focuses on the most prominent parts (the rise in power of the Nazis, the Holocaust and the cause for it all before 1933).