Yeah, I think this was probably the logic when I was taught about it, as I recall there were a couple who did have their parents excuse them and one or two who excused themselves when they were told the disclaimer at the start of the lessons. Dunno what they did, draw pictures of Jesus or something probably.
In the US, most black victims of crime are the victims of black criminals. This might well vary somewhat in some locations, but overall black-on-black crime is more common than white-on-black crime - which, I hasten to add, isn’t OK and that doesn’t mean that some white-on-black hate-fueled crimes are particularly vicious.
Also, as pointed out, despite the similarities in skin color the Nazis did NOT view Jews as the same race. In fact, there are a lot of non-Nazis that don’t view Jews as white people, either.
I’m not Jewish at all, but I’m pretty sure we learned about it by 11. Nothing really specific, of course, but just that Hitler killed Jews in some long ago war called World War II. I can’t remember the book we were read in class about it. It involved a girl hiding with a German family who pretended she was their daughter, and some necklace with a Star of David or other recognizably Jewish symbol that the girl kept hidden.
And I don’t really think there was a problem with that. I’d actually recommend it around the American Girls’ book age, which is age 9. Again, not anything too specific or graphic, but the basic idea is something you can understand at that young age. You don’t have to make it scarring.
I don’t remember ever not knowing about the Holocaust. Somewhere around 7th or 8th grade, a Holocaust survivor gave a talk at my school, and I wasn’t particularly surprised by the information. That might have been the first time it was broached in an educational setting for me. But I picked up a lot from pop culture representations.
I do have an oddly specific memory of when I learned about the tattoos, though. There was a fairly crappy movie called The Monster Squad, about a bunch of kids fighting the Universal Studios monsters. There’s one scene where the old guy who’s acting as their Van Helsing stretches out his arm, and you can see a series of numbers tattooed on it. I remember asking my mom about it, because the movie made it clear that they were significant somehow, but they didn’t actually figure into the plot. I did already know about the Holocaust, though - just not that detail of it. I would have been about twelve when the film came out.
Going back a bit earlier, I had an older friend who collected horror comics. This would have been the tail end of the horror comic resurgence, so somewhere in the early '80s. One of the comics had a story about a concentration camp where the blood and flesh and… other stuff from the murdered Jews spontaneously coalesced into a golem that killed the Nazi guards. Probably was under the age of ten or so when I read that one, and I know I already understood the general context of the Holocaust.
I probably learned about it at the same time my parents did, since it occurred during my lifetime.
I think the more salient question is HOW should it be taught: As a unique, singular even that stands out separate from all other historical events, or just another of the events over several millennia in which humans abuised power.