If you passed by Chinese schools on Friday or this past weekend, you would probably have seen some middle-aged women waiting outside with anxious looks dressed in traditional Qipao dresses.

They were not part of a flash mob performance, but instead, mothers who wished to bring good fortune to their children taking the national college entrance exam, also known as the gaokao.

"A green dress means green lights all the way," said 44-year-old Zhong Yan, who waited for her daughter in a green Qipao dress on Saturday outside a test center in Kunming, capital of southwest China's Yunnan Province.

Zhong bought three Qipao dresses a month before the exam, costing over 3,000 yuan (about 434 US dollars). The dresses are green, red and yellow, all auspicious colors in Chinese culture.

"I wore red on the first day, which means we're off to a good start," she said. "I will wear the yellow one on the last day because it symbolizes a bright future."

Zhong is among an increasing number of Chinese mothers who choose to wear the traditional Chinese one-piece dress for their children's gaokao.

Official data showed that more than 10 million high school students across China applied to sit this year's exam. It is deemed by many as the most important event for the students.

"We need a sense of ritual on such an important occasion," said Ye Youling, a mother who ordered a tailor-made Qipao dress a month before her son took the gaokao. "A Qipao might be too solemn in daily life, but it's the best outfit for the gaokao."

Ye said she had been working out regularly to fit into the tight-fitting Qipao dress. "I want to tell my son that I'm working just as hard as he is and that I'm rooting for him."

For Liu Dan, president of the Yunnan Traditional Chinese Costume Association, wearing a Qipao during the gaokao is not so different from other traditional Chinese rituals, such as putting on spring couplets during Spring Festival and wearing red for weddings.

"Qipao, elegant and solemn, sounds like a Chinese phrase for victory. It goes well with the gaokao," Liu said.

The popularity of Qipaos among the mothers of exam-takers has, without doubt, boosted the sales of Qipao dresses in the days leading up to this year's gaokao.

Miyingqipao, the owner of an online Qipao shop on Taobao, China's major online shopping platform, told Xinhua that his shop sold more than 100 Qipaos in the past month, most of which were red.

"Usually, not so many people buy red Qipaos. It must have something to do with gaokao," he said.

In a brick-and-mortar Qipao workshop in Shanghai, the owner had to hire 20 more dressmakers last month to meet the surging demand for Qipao dresses.

"In the past, Qipaos were usually worn as a formal dress for diplomatic occasions," said Liu Dan. "Their growing popularity in China shows Chinese people have become more interested in traditional culture."