TOKYO – Nearly half of Tokyo high schools ask students with hair that is wavy or not black to submit certificates confirming that their hair is not artificially altered, public broadcaster NHK has reported.

Of 177 high schools run by the Tokyo Metropolitan government, 79 ask for these certificates signed by parents, NHK said on Thursday, citing information the Japanese Communist Party obtained from the metropolitan government.

In Japan, many schools have strict rules about hair, accessories, make-up and uniforms. Some, for instance, forbid nail polish, leg shaving or layering of boys’ hair. Teens who streak or color their hair over the summer have to re-dye it black in time for “moral inspection day.”

Tokyo’s board of education told NHK that the hair certificates are not compulsory. But the broadcaster said only five of the 79 schools make it clear in writing that students aren’t required to submit them.

The NHK report comes a week after a Japanese court ruled in favor of a public high school that was sued in a case involving the color of a student’s hair.

The student said she stopped attending Osaka Prefecture Kaifukan Senior High School after teachers pressed her to dye her hair black, though it was naturally brown. She was seeking more than 2.2 million yen, or about 20,000 U.S. dollars, in damages.

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The Osaka District Court said that the school’s rule banning dyed hair is reasonable, and it implied teachers could have legitimately thought the girl had dyed her hair brown because the roots were black.

The court, however, ordered Osaka Prefecture to pay about $3,000 in damages because the school removed the girl’s name from the roster when she stopped coming to school.