Cassidy, previously known as Lance, said she knew she was a girl from a young age. She'd gravitated toward Barbie dolls, lipstick and dresses and was excluded by male classmates for years because of it.
In middle school Cassidy told classmates she was gay to try to blend in. It wasn't until her sophomore year that she publicly dressed as a girl — on Halloween.
This year, as a senior, she came to school as herself.
The school's staff encouraged her and she received mostly positive responses from students.
On Friday, her classmates chanted her name as she walked over to accept her prize in a green and pale pink gown.