This young lady, Amari Williams was going to her first and only prom. She even saved her money to go however she was turned away. She had her dressed customer made for what it seems that everyone gets ready for during their Senior year. The principal told  Williams her prom dress wasn't "in accordance with the events's dress code. Why? ..the official reason," Williams' ankle was showing.
Here is Williams statment on the matter: 

“The dress code, when I looked over it, it did mention that the dress had to be floor length, and they considered it not formal since it wasn’t the same length all the way around. But then I brought it to [the principal’s] attention that some of the rules in the dress-code policy also state that midriffs, high splits, or low back dresses aren’t allowed. As I’d been standing there, I saw she’d been allowing all those types of dresses into prom, but here she denies my daughter, and she’s dressed appropriately, not showing any skin or anything inappropriate at all. Her response to me was she used her own judgement.”

Read more at: The Black Loop