A question that every parent dreads
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Lessons in life
With more sex shops opening in streets and shopping malls across China, the unwillingness of Chinese schools and colleges to delve deeper into sex education appears conflicting.
Professor Chen said he believes teaching sex in the classroom is as much a taboo as it was when he started his course in 1995.
At the time, many questioned why he was willing to risk his reputation by leading such a "vile course". Even as he was compiling a book on his practices a decade later, Chen's editor suggested its diagrams be printed only in black and white.
Zhang Yumei, a retired teacher of sex education at the experimental school affiliated with Capital Normal University, recalled that her colleagues used to accuse her of giving children "the wrong idea", while parents of students claimed the textbooks she provided contained "antisocial" content.
"When I taught on the use of condoms, some teachers said it was improper as they themselves had never been taught about that," she said.
China's education system mainly evaluates the abilities of students through examinations. However, there is no test for sexual knowledge. This has, in part, created an information vacuum, with older generations unable to pass on education to youngsters.
"Teachers and parents do not know how to teach (about sex)," said Liu Liqing at Marie Stopes International, an NGO that provides sexual and reproductive healthcare.
Despite improvements brought about by a greater public awareness of HIV and AIDS in recent years, she said sex education is still not sufficient - or even available - in most schools, with the situation most acute in rural and underdeveloped areas.
In impoverished regions, many leave home for large cities after graduating junior high, "so their knowledge on sex lags behind", said Liu. "As they migrate, their unhealthy condition could threaten the wider population."
She also argues that the central government's policy of blocking online access to all pornographic content (porn is illegal and is subject to constant crackdowns) is not the most effective way to prevent children from committing sex-related crimes, as many have suggested.
"Equipping them with the proper knowledge would be far more useful," she added.
Li Jinyan, mother of a 12-year-old boy at No 3 Primary School, burst out laughing when she was asked whether she has educated his son about the facts of life. "Why should I?" asked the 40-year-old housewife. "They will be taught about it in biology classes when they enter high school."
Xiong Baohua, who also has a son in sixth grade at the school, said her child, who has just started puberty, is simply too busy to be distracted. "I hardly talk to him about anything except his studies. He has lots of homework to do and extra classes to attend during weekends," she said, before confessing she feels "shy about the prospect of discussing sex".
Even professor Chen admitted he never taught his two daughters about the birds and the bees.
"There were plenty of books at home and they were free to read them," he said, although he did discourage open discussion about sex in his classes. "It could have led to some improper and awkward situations."
Wang Xuejing, a mother of twin daughters aged 11, does not have the same reservations, however. She told her daughters about reproduction when they were in kindergarten.
"I'm ready to teach them about safe sex when they get to high school. You can't simply avoid talking about sex when there are so many teenage pregnancies," she added.
