In 2019, Judge Malcolm J. Howard of the U.S. District Court for the Eastern District of North Carolina struck down the uniform policy as unconstitutional, saying the skirts requirement “causes the girls to suffer a burden the boys do not, simply because they are female.”

In 2021, a panel of three judges in the U.S. Court of Appeals for the Fourth Circuit reversed the district court’s judgment, court documents show. That decision was vacated by a vote by the full court of judges, who, in the most recent appeal. had to determine if the charter school was a public entity, the documents show.

Charter Day School, a tuition-free school of more than 900 students in southeastern North Carolina, argued that it was private and, therefore, that the Constitution’s equal protection clause, which protects individuals from discrimination by public entities, did not apply.

But the school receives 95 percent of its funding from federal, state and local government authorities, the judges said, and it must follow the same guidelines as public schools, which are prohibited from enacting discriminatory dress codes. While the court settled the question of whether Charter Day’s dress code violated the 14th Amendment, a district court will reconsider whether it also violates Title IX, which prohibits sex-based discrimination, at a later date.

Galen Sherwin, a senior staff lawyer at the A.C.L.U.’s Women’s Rights Project who represented the plaintiffs, said even though the ruling was limited to North Carolina, she believes that it could have broader implications for dress codes elsewhere.

“It’s very significant on the question of the charter schools and the availability for constitutional protections,” Ms. Sherwin said about the ruling in a phone interview. “Certainly it should put public charter schools across the country on alert that they should be expected to comply.”