Stargirl starts on the first day of eleventh grade for our narrator, Leo Borlock. The buzz around the school is, “Did you see the new girl?” Stargirl goes to school for the first time as a tenth grader. Up till then, she had been home schooled. Due to Stargirl’s unusual behavior including carrying her pet rat to school, singing while playing the ukulele at lunch, wearing strange clothing, and so on, most students peg her as an outcast even though she is extremely friendly to everyone. Leo develops a crush on Stargirl. He even follows her one day after school just to see where she is headed. He discovers that she is delivering a congratulations card to a stranger.
After attending a football game in which Stargirl runs across the football field playfully cheering and stirring up the crowd, she is asked to join the cheer leading squad. Students began to like her. At this point, students love Stargirl’s upbeat, quirky actions. People begin attending the football games, not to watch the game, but to see Stargirl’s playful antics including cheering for the opposing team. By Thanksgiving, Stargirl is the most popular person at the school.