I did a degree in history a few decades ago, and more recently, in relation to how DC are taught for example, I have noticed what you say. It applies to other areas of the world such as Soviet Union, there are huge areas left untaught - it wasn't so much that we were taught to look at the history positively - neither positively or negatively in fact - more that we were taught about all relevant aspects of Soviet history, not exclusively about purges, all of which is interesting and important and extremely relevant to the rest of the world. Also in relation to the subject of the thread, I see now the history of both the modern conflict and earlier history of the area will sometimes leave out huge chunks of relevant information.
I get the impression that it depends on the teacher. In the UK, history is supposed to be taught without bias. I know in some areas of the world what is taught is prescribed. And how our media now presents things is biased to the point of being meaningless in relation to certain subjects.
There seems to be a downward spiral in terms of education standards in some areas. But not across the board, it depends on the individual school and other factors. And government policy about specific areas, which changes with the wind.
On the other hand, certain specific and discrete areas of education have well funded interest groups, lobby groups. Perhaps this is affecting everything.