My belief--for what it's worth:
There should be progress over the year. I have found that the lower level books can be really stupid--how can a kid develop a passion for reading when they're facing such inane stories (many times with poor grammar)?
My suggestion is to use the summer to visit the library and take out lots of fairy tales (from all different countries/cultures--our library has them divided into Native American folk tales, Russian, Asian, English, etc.). We must have read the Cinderella story at least a dozen different versions. Take out 20 at a time (10 fiction and 10 nonfiction about plants or animals or biographical profiles). Read to her and make it really fun.
Also get out books for her to read (I really liked the numbered books (Step? 1-4). On things like Pompeii, Snakes, Dinosaurs, the Titanic. Really help her look so they're not silly. Our summer goal was 100 books--keep a list on fridge recording book title.
I believe reading is the most important skill to be successful later on, even for math/science strong kids. It's so important to nurture love of reading and reflecting about what you've read. The AR system doesn't do much for reflecting, but if you're working together over the summer, she'll learn to do it on her own for next school year.
