Talked with a friend who is a teacher about this last weekend...
According to him, teachers are highly encouraged to tie material in one subject to that in another subject. By repeatedly exposing students to the same information/concepts, they feel it improves retention.
That's all these teachers were doing (I believe I read somewhere that the math problems were tied to other lessons about Frederick Douglas). Taken out of context, it looks horrible, but frankly, I don't think the teachers did anything wrong...at least not enough to lose their jobs over. But when a story like this hits the media, heads gotta roll...