When Shirley's parents decide to adopt a Vietnamese baby boy as their own, Shirley is mildly happy that her parents attention will no longer be on her. However, when a mix up results in the possibility of having slightly older younger sister instead, Shirley becomes excited with the prospect of being able to teach and help someone learn how to speak English and about American culture.
Shirley's new younger sister, newly named "Jackie", soon becomes devoted to Shirley and eager to learn from her older sister and they become fast friends. But when Jackie ends up excelling in school and moved from the regular third grade class to an advanced one, Shirley begins to feel threatened and jealous that Jackie will no longer need her and once again, Shirley will be useless and unable to succeed.
When she stops making an effort at school, an unexpected challenge arises in the two sisters' relationship and forces Shirley to come to terms with her role as Jackie's sister and beginning to understand her own strengths. With extra help from the school resource room, Shirley begins to succeed in school in her own way.