TOKYO (NYTIMES) - Like many schools in Japan, where most people are born with straight, black hair, the Kaifukan Senior High School in Osaka is fussy about students' appearances. Perms and braided extensions are off limits, as are dyed and bleached hair.

One brown-haired Japanese-born student ran into trouble when school officials, believing that she had flouted the rules, checked her roots and repeatedly demanded that she dye it black. Though the student dyed her hair at first, she eventually stopped complying.

The school then removed her desk from the classroom, erased her name from school rosters and barred her from a school trip. In 2017, when the student was 18, she sued the Osaka prefecture, which runs the school, alleging mental distress.

On Tuesday (Feb 16), the District Court of Osaka ordered the local government to pay her US$3,100 (S$4,100) in emotional damages. The student had originally sought US$20,780 in damages.

But in a statement denounced by student advocates, the judge also ruled that the school's enforcement of appearance-related regulations did not run afoul of the law, and that there were "reasonable grounds" to believe that the student had naturally black hair.

The case set off a national reckoning over invasive school rules and an outcry against regulations that left little room for student individuality. Activist groups started petitions demanding changes to rules that dictate the length of students' hair, skirts and, in some cases, the colour of their underwear.

Japan is not the only country in the region, however, to police hair colour in young women.

Last year, two women's soccer teams at Chinese universities were barred from participating in a match because players had dyed hair, which was against the rules. When one player was judged not to have "black enough" hair, she was ordered to leave the game, forcing her team to forfeit the match.

Professor Kayoko Oshima, a professor of policy at Doshisha University in Kyoto, Japan, said in a television interview on Tuesday that some school rules were necessary, but that in this case, "the hair guidance caused the girl to avoid going to school and took away a learning opportunity".

Prof Oshima added: "In this era, when there are global interactions with people who have different eyes and hair, is it reasonable for schools to ban dyed or permed hair? We have to reconsider."

According to a plaintiff's petition filed in 2017, the student's mother told the school that her daughter had naturally brown hair. But teachers kept pressing the student to darken her hair.

She applied black dye so often that she developed rashes and scalp pain before she stopped going to class in September 2016 because of the stress.

The Osaka government argued that a vice-principal had inspected the student's roots and had found them to be black, which the school interpreted as evidence that she had been colouring her hair.

The student, who has not been identified, could not be reached for comment. Neither could her lawyer, Mr Yoshiyuki Hayashi, who said in a news conference on Tuesday that he would appeal the ruling. He said that the court had erred in determining that the student's natural hair colour was black.

In the court ruling, Judge Noriko Yokota criticised the Osaka high school for scrubbing the student's name from school records, saying that "its actions lacked serious legitimacy".

But Judge Yokota rejected the student's claim about her naturally brown hair, adding that the regulations on student appearance served a legitimate purpose and that it was reasonable for the school to provide "hair guidance" and to conduct inspections to make sure those rules were followed.

In the wake of the lawsuit, the scrutiny applied to Japanese school rules has led to modest changes in some schools since the case was filed.

As of 2018, 40 per cent of public high schools in Osaka prefecture have reworded rules explicitly banning brown or curly hair, replacing them with prohibitions on hair that was "intentionally" dyed or permed, Osaka's education board said. And in 2019, Tokyo's education authorities barred schools from instructing students with lighter hair to dye it black.

The principal of the Kaifukan Senior High School, Mr Masahiko Takashi, said on Tuesday that rules for hair appearance remained the same at his school. He said he would try to explain the school's intentions to students and parents.

"When it comes to students with dyed hair, I have not changed the standards for students to change it back to black," he said at a news conference. "But I want to take this lawsuit as a lesson and provide fine-tuned guidance for my students."