I thought reading Lord of the Flies was a bit much for 9th grade when we had to read it. There were some inappropriate stuff in it and I went to Catholic School.
I substitute taught in three different high school English classes during a unit in which Lord of the Flies was being taught. In each one, I asked the kids if their teacher had explained that the expression "lord of the flies" is a translation of Beelzebub, the Hebrew nickname for an ancient Semitic god that is also used as an alternative name for Satan. In none of the classes were the students told that.