When 15-year-old Leia Lai and two of her classmates went back to school on Monday, they sported a new look - bald.
The three St Margaret's Secondary School students had cut their hair to raise funds for a cancer charity.
But this drew the ire of their principal, as they had not donned wigs, as they had promised earlier.
The school's rules do not allow "punk, unfeminine or sloppy hairstyles". Said principal Marion Tan: "It's very clear in our mission: it's about their turnout as a young lady."
And if the girls were allowed to go bald, others might take advantage.
"Can you imagine if I were to say yes, I'd have everybody coming to school with a bald head. Sometimes it's a fad, so they would take advantage of the situation."
A group of five girls had asked for permission to take part in last Saturday's Hair for Hope event to raise funds for the Children's Cancer Foundation, and all five had promised to wear a wig. But only two of the five Secondary 3 students kept their word.
So the other three were called out of class and taken by a parent volunteer to buy wigs that cost around $70 each. The principal said promises made should be kept.
But the students and parents, including Leia's mother Emily Chia, argued that covering up was against the spirit of Hair for Hope.
Said Madam Chia, 41: "The purpose of Hair for Hope is to show children with cancer that it's okay to be bald."
Mr Wong Choon Yew, the father of Cherry Wong - one of the three students - said he respected the principal's wishes. "Whatever the girls have agreed, they have to abide by."
But the 44-year-old pastor also said the shorn pates "are public testimony that shows support and raises awareness of cancer patients to their schoolmates".
Three other schools, whose female students took part in Hair for Hope, told The Straits Times that students were allowed to go bald.
As for Leia and Cherry, they have been allowed to go to school bald. But only because of doctors' notes certifying they had rashes on their heads from wearing wigs.