The curriculum doesn't have to be a problem, if the teacher wants to bias the lesson. For example looking back at it my history teacher, whom on the whole was one of my favorite teachers, was super pro-Israel. However I didn't realize this until years later and as result I was probably in my mid 20s before I started to get even a slightly nuanced picture of the whole situation in the Middle East.

Now there was nothing in the curriculum that said "Students must learn that Israel can do no wrong" it was just the way he chose to bias his presentation.