There is something about an animal protagonist that draws kids in- I don't know if they relate to the animals in a specific way, if it's the cuteness, if it's the otherness while still being familiar- but these are sure to be wins with your elementary reading level kiddos. Enjoy!
The Miraculous Journey of Edward Tulane, Kate DiCamillo
Mrs. Frisby and the Rats of Nimh, Robert C. O'Brien
The Wind in the Willows, Kenneth Grahame
The Rescuers, Margery Sharp
The Trumpet and the Swan, E.B. White
The Wild Robot, Peter Brown
Charlotte's Web, E.B. White
My Father's Dragon, Ruth Stiles Gannett