There are many documentary -archival type works out there that make the Nazi era's sickness clearly visible to any person with concience or working brain. I can't imagine that school requiring the "R" and "X" versions to be used to make the point. The "G" and "PG" versions are more than adequate in communicating the Nazi horrors,
It seems to me if the kids are having nightemares, etc they are not as "jaded' about violence as the school board thinks they are. I say school board because that teacher has to provide a 'lesson plan" that identifies the media materials required to do the class work. The local board is responsible for content, however, they may not know what is being required in a classroom at all times.
Bottom line is that the TAXPAYER is the customer in a public school system and if the TAXPAYER feels it is not appropriate the TAXPAYER needs to speak up and be heard.
I think that "reality" based war fiction is a great thing-but may not be OK for kids. The level of graphic depiction found on say, The History Channel is more than enough for public high school.
Just my 2 cents worth.