Zardnaar
Legend
The school I work for has us teaching about the history of slavery and the treatment of Native Americans at the primary level (7-10 years old). It's not graphic, but the education system is not shying away from difficult topics.
Ours was probably a bit more graphic. The WW2 book was middle school/intermediate (age 10) highschool had adult books in the library (age 12)
History class was second year (age 13 turned 14). And the video we watched was quite graphic.