Zoe Brock, from Houston, Texas, looked raring to go as she posed in her Christian academy uniform for a photo outside her 14-year-old brother Sam's high school.
Her mother Sharvonne Broussard, 36, sent the picture of Zoe to her niece Alexis who shared it on Twitter where she has inspired tens of thousands with her enthusiasm.
The picture of Zoe, who started Triumph Christian Academy last year after her second birthday, was taken on Monday. Since then it has been liked by 67,000 Twitter users and shared by 32,000.
She told Daily Mail Online: 'Miss Zoe was excited about the first day of school from the time she woke up. She is naturally an enthusiastic child with a great personality.
'Every morning, even on the weekends she wakes up ready to go to school to see her teacher and friends so I am almost certain this enthusiasm will continue throughout the school year.'