A Straits Times report about three St Margaret's Secondary School students who were forced to put on wigs after shaving their heads for charity has garnered strong reaction online.

Most netizens felt that the school's regulations were too inflexible and applauded the girls for their bravery and compassion.

Many were also forgiving of the girls breaking their promise to their principal, who had said they could shave their heads as long as they wore a wig to school.

A common sentiment was that forcing the girls to don wigs after shaving their heads in support of cancer patients defeated the purpose of what they did. Others felt that femininity should not be determined by the length of a girl's hair.

"It is a serious affront to the spirit of charity and an insult to other women who did likewise in support of Hair for Hope," said Au Kah Kay on The Straits Times' Facebook page. The story was shared about 40,000 times on Facebook with about 200 readers posting their comments on the Straits Times website.

The girls had shaved their heads last Saturday to raise funds for the Children's Cancer Foundation. They got permission from their principal, on condition they would wear a wig to school. But only two of the five Secondary 3 students kept their word.

The other three were called out of class and taken by a parent volunteer to buy wigs. The principal, Mrs Marion Tan, said promises made should be kept.

Some netizens chided the three students for not keeping to their promise to their principal. A hashtag, #isupportmrstan, has also emerged on Twitter in support of the principal.

Meanwhile, some other schools have allowed their female students to shave their heads for the charity event without having to don wigs. At SJI International, for example, staff members and students, including girls, shaved their heads for the event.