I read them Olivia by Ian Falconer. If you don't know this book, you are seriously missing out on some major cuteness. In the book, Olivia (the pig) goes to the museum and sees some Degas ballerinas and "Autumn Rhythm #30":
I asked them what this was a picture of. One girl said, "Ballerinas!" A boy said, "Spiders!" Another boy ran up to the front of the class so he could take a closer look at the book and decided, with all seriousness, "War."