Maybe that is the explanation. They take the STAR test to get the reading level for the books they read. They then take AR tests on the books. If they have the exact same books in the library, though, and she was getting 90 or 100 percent on every test (even if she did get higher level books), then does it make sense to set back her level?

The changed norms must be the explanation. That seems like a really big change, but at least it makes more sense.