Um, what seems to be the issue? I see it for what is was, not what one wishes to turn it into.
A classroom project to show what was outlawed when the Nazi's were in power. Did the students throw in the flag and made a error, sure, I don't see any ill will behind the poster.
Denmark was occupied by Nazi Germany during most of WWII. Don't have a clue about the cupcakes... Hitler banned shechita, maybe something to do with food items?