A Mississippi high school senior, whose initials are L.B., said she was looking forward to finally walking across the stage and receiving her diploma at Harrison Central High School's graduation ceremony over the weekend.
L.B., a transgender girl, had already picked out a dress and a pair of heeled shoes to wear under her traditional cap and gown.
Earlier this month, however, she said she and her parents were informed by Harrison Central principal Kelly Fuller that she could not attend the ceremony because her outfit violated the school's male dress code, which requires that boys wear black suits.
"I had dreamed of walking across the stage in my beautiful white dress that I purchased months ago in preparation for this event," L.B. said during a speech Monday afternoon in Washington, D.C. "This is very humiliating, discouraging and disappointing to hear."
The American Civil Liberties Union and the ACLU of Mississippi have since filed a lawsuit against Harrison Central School District on L.B.'s behalf. But a federal judge denied L.B.'s request to wear a dress at her graduation in a late Friday night ruling after an hours-long emergency injunction hearing.
Harrison Central School District did not immediately respond to ABC News' request for comment.
Just days after the ruling, L.B. was one of more than 100 transgender young people, ranging from age 5 to 20, who gathered at the nation's capital Monday afternoon for the first-ever Trans Youth Prom in defiance of mounting attacks on their rights across the country.
"Today we are here, united, doing what's right, and stronger than ever before," she said. "Together one by one, state by state, vote by vote, we can construct a better world. Transgender youth have always been here, and rest assured we are here to stay."
The event, held near the Capitol Reflecting Pool on the National Mall, was conceived as an occasion to celebrate the "brilliance, love, joy, and liberation" of transgender youth, organizers said.
Adding a "lovely and lively queer twist on prom," the event featured vibrant music and dancing by artists including drag performer and emcee Stormie Daie, as well as DJ and transgender activist Nico Craig.
The historic gathering was the brainchild of trans youth organizers Daniel Trujillo, 15, Libby Gonzales, 13, Grayson McFerrin-Hogan, 12, and Hobbes Chukumba, 16.
"Trans Prom is a celebration of affirming love and support. It is trans joy in full display," Trujillo said at the event. "We are proud. We are visible. We will not be erased. And we courageously stand here today in defiance of those who say we are too young to know who we are."
Since January, state legislators across the nation have introduced nearly 500 anti-LGBTQ bills, according to the American Civil Liberties Union, including limitations on transgender kids' participation in sports, bans on gender-affirming care and restrictions on trans access to bathrooms.
More than 15 states -- most recently, Nebraska -- have already successfully passed laws restricting gender-affirming care for minors.
A January poll conducted by the Trevor Project found that 86% of transgender or nonbinary youth reported that recent debates around anti-trans bills have negatively impacted their mental health.
Against the backdrop of these crises, Chase Strangio, deputy director for Transgender Justice and staff attorney with the ACLU, said the Trans Youth Prom was a reminder of the "networks of support" the LBGTQ community has historically built for its own survival.
"If they try to take away our health care, we will get each other health care. If they try to take away our books, we will make our books available," Strangio said. "And if they to cut off our history by cutting us off from ourselves, from our elders or from our youth, we will tell our stories over and over again."