(NewsNation) — Chelsea Mitchell says that as a high school senior, she was the fastest girl in Connecticut. But she believes running against transgender athletes made it an unfair fight.

“I competed against two biological males all four years of high school,” Mitchell said. “I lost out on podium medals. I lost two all-New England awards, and then eventually, I lost four state championships to these two males.”

She says she lost 20 times throughout her career to these competitors. It’s why while she was in high school, she anonymously filed a Title IX complaint against the state and its policies.

The next year, Mitchell, along with three other female athletes, filed a lawsuit against the Connecticut Association of Schools, the athletic conference and boards of education in Connecticut.

“Everyone deserves to participate in sports, but it’s about where it’s most fair. In my experience, it was completely unfair to put these athletes in the female category, because we know there are biological differences between men and women,” Mitchell said, later adding: “If they’re going to say they have no advantage, we might as well just have one big category.”

Attorneys with the conservative group Alliance Defending Freedom, took on the lawsuit. Attorney Christina Kiefer says the case is about “restoring basic fairness and a level playing field” in women’s sports.

“We believe that it’s really clear males have inherent physical advantages over females that makes it unfair to force girls like Chelsea to compete against males in their sport,” Kiefer said.

With the suit, they are trying to overturn a policy that allows transgender athletes to compete in accordance with their gender identity, regardless of their biological sex. Now, their case is being heard in federal court by the Second District.

The ACLU and other advocacy groups have challenged the lawsuit.

“Every student deserves to be treated with dignity and respect. This includes transgender girls of all ages and in all sports, without exception,” Kelly Robinson, the president of the Human Rights Campaign, said. “All transgender students should be presumed eligible to participate in sports consistent with their gender identity.”

Mitchell insists the “female category needs to be protected.”

“It’s not fair to make us run against biological males, and so that’s really my motivation behind this. It’s just protecting the female category,” Mitchell said.

The case will be heard on Tuesday in the Manhattan District Court of Appeals.