It's shocking that in 2012 not a few parents still tell their children that they were found in garbage bins or, more pleasantly, in gardens.
Teaching about the birds and the bees is still very sensitive in China, and whether schools should teach, what and how much they should teach, and when are still hotly debated. Many parents fear sex education is "how to" education.
But rising rates of teen pregnancy are making people think again whether no education about sex is best.
There now appears to be a general consensus that public education has a role to play in giving students some biologically accurate education, as well as conveying values and concepts of appropriate behavior.
Sex education is still in an experimental phase in Shanghai.
Last week new sex education textbooks with colorful illustrations and interesting games were distributed to more than 100 primary schools - for the first sex education in the city's primary grades.
The books, "Boys and Girls," were used in a pilot program in 18 primary schools last year, generating considerably controversy. Most parents, who themselves received virtually no sex education at school, welcomed the move, while some said the content was too revealing.
In a chapter called "Where Do I Come From?" the textbook introduces names of private parts and explains fertilization with colorful illustrations.
"No, you cannot touch my private parts!" Primary school students are taught to say this loud and clear. Using drawings and cutouts of boys and girls, they put green and red circles on parts of the body that can and cannot be touched by other people.
"We have forbidden zones on our bodies. The parts of a boy or girl that are covered by swimsuits are the private parts," the book says.
Students enjoy learning, drawing and coloring. One teacher says her students were quite serious and no one giggled.
The idea is to present the information at an early age in a straightforward, factual way, not as something dirty or to be ashamed of.
The books are based on the sex education materials of the Primary School Affiliated to the University of Shanghai for Science and Technology. Different grades use books with different content that progresses gradually.
In the past, schools included some superficial sex education health classes, but there were no dedicated textbooks.
Teachers themselves have gone through an 18-month training program on how to use the new textbooks and present in the information in an interesting and factual way.
In addition to textbooks, the publisher, Shanghai Education Publishing House, compiled a family edition available at bookstores to help parents answer the question, "Where did I come from?" Parents and children can read it together.
Time and again, young adults born in the 1970s and 1980s say they were told they came from garbage bins or from under cabbage leaves. Many parents feel awkward and don't know how to introduce and explain the subject, a little at a time, depending on what's appropriate. Many parents are afraid that children want to know everything when at first they just want a simple answer.
"It's a pity that we, born in the 1970s, did not receive this kind of scientific sex education," says Wang Dongdong, a mother with a school-aged child.
Sharon Gong, whose daughter is in primary school, says, "Children have easy access to sex information online nowadays. It's important to teach them the right things."
Compared with Beijing's sex education textbook, which for upper grades contains illustrations of sexual intercourse, the Shanghai version is tamer and uses cartoons of tadpoles. Some education departments from around the country have contacted the publisher to buy copies.
Not everyone is convinced.
"Do children need to understand so clearly?" asks 25-year-old John Yang. "Why not let them keep their innocence longer?"
Today children mature earlier and the world is filled with sexually provocative media, advertising, entertainment and fashion. Experts say it's important that children know how to understand the changes in their bodies and to evaluate the information around them, without looking for answers online or from young people who may know too much at an early age.
According to 2009 statistics from the Chinese Medical Association, Chinese girls typically begin to enter puberty when they are just over nine years old.
Xu Jing, one of the textbook's editors and vice principal of the Primary School Affiliated to the University of Shanghai for Science and Technology, says children's perspective is very different from adults' and they absorb information about sexuality just as they take in other information.
She advises parents to convey information about sexuality and reproduction in a factual way, as a normal part of life, and not to hide it, make it mysterious or shameful. If children's questions are unanswered and they become curious, they will go looking for answers and they will find them, she says.