I don't remember when I first read this book; it had been so long ago. I was probably around second or third grade. For a little girl who knew what bullying was but didn't understand it, this book helped a lot. This was also the first book I read where I didn't approve of the main character's actions. The narrator was just as much of a bully as Wendy because she saw what was going on and let all this happen. The original victim of the bullying, the girl whose nickname was "Blubber" because of her report on whales, ended up becoming the bully's helper when she switches positions with the main character. This helped me learn about hiarchy in popularity and how easy it is to become a bully. It also taught me not to be friends with popular girls, because they could be just as mean to you. Judy Blume is an awesome author; her books can teach so many things to kids and adults alike.
I would specifically recommend this to preteen girls, but that's just a suggestion; not a limitation. Anyone who likes this genre of books should read it.