Holocaust Units: What Age?

So like many other students, in school several teachers did units on the Holocaust. After reading Maus, I started thinking about the first time I learned about WW2 and the Holocaust. I believe it was in 7th grade. We learned about it in my 7th grade History class for the majority of the year. But then in my 8th grade English class we read and discussed The Diary of Anne Frank. However, at 12/13 years old is that a good age to be able to grasp the severity?

I think that it is a very appropriate age. I do remember some kids making jokes about Anne Frank's diary and how upset the teacher got, which showed that kids are immature. But then again, maybe a serious unit such as Anne Frank can develop kids understanding and make them somewhat mature? An assignment that usually followed though was a diary assignment. It made us connect with Anne but I always found it difficult to write because my entries seemed shallow compared to her struggles.

All and all, I think 13 is the perfect age for Holocaust units and I believe they should be done in both History and English classes to show the significance of the events.