The Double-Digit Club by Marion Dane Bauer, 2004

Nine-year old Sarah dreads the first day of summer when her best friend Paige turns ten and will be invited to join the exclusive double-digit club (DDC). She prompts her on what to say when the event happens, but of course, Paige backs down, and goes with the DDCs. Sarah is crushed, and spends time reading, moping, and eventually visiting her next-door neighbor, old blind Miss Berglund. One day she sees a beautiful doll in Miss Berglund's bedroom, one that could win back Paige's friendship. She "borrows" the doll, shows it to Paige, and in a scuffle, the doll is broken. In the end, Sarah confesses to Miss Berglund in a heart-to-heart and she learns that growing up is about more than turning ten. It's a perfect example of the writing equation: protagonist + problem + solution = story. Textbook story arc.