Lexile Level: AD410L
The rainbow fish is the "most beautiful fish in the entire ocean" and he refuses to share his gills with any other fish in the sea. The rainbow fish's selfishness isolates him because no one wants to be his friend. Later on, the rainbow fish asked for advice from an octopus and then the fish "discovered how to be happy" by sharing his sparkling gills with his friends.
I would use this book to teach my students how to share.