My son had this issue in junior high, almost every "literature book" they did in 7th & 8th grade was something he read in 4th-6th. In the lower grades they were books he chose for their monthly book reviews, or the small group literature that was done in 6th. It made the teachers lessons on "predicting" the ending not very useful, and it is a skill my son is still struggling with. And my son found it boring to have to slowly go through the books a second time. Books that this happened to were Animal Farm, and Fahrenheit 451, and one or two others I don't remember right now.
This is why I sometimes suggest holding off on particular books when kids are particularly young. And waiting till they can really appreciate it. I personally do enjoy re-reading my favorite books. And I can see that kids get different things out of books when they are read at different ages, but I also have seen kids with the attitude of read that once I don't need to read it again.
