Final answer:
In the book 'Wonder', Summer Dawson is the girl who sits with August at lunch on the first day.
Step-by-step explanation:
In the book Wonder, the girl who was the only one to sit with August at lunch on the first day is named Summer Dawson. This kind gesture by Summer marks the beginning of a friendship that plays a significant role in the book. Despite the challenges that August faces due to his facial differences, Summer's acceptance and kindness towards him underscore the themes of empathy and friendship that are central to the story.