The ?first sex education textbook for pupils in grades one and two will be introduced to local classrooms this semester.

Compared with the Beijing sex education textbook that has sparked controversy, the Shanghai version is more implicit as it has replaced illustrations depicting intercourse with cartoon pictures of tadpoles.

However, many parents still worried that it's too early to teach sex information to children under the age of 10 and complained that the book is too revealing.

In one chapter called "Where do I come from?" it introduces names of private parts and explains fertilization with colorful illustrations.

"Kindergarten children have a vague idea about gender difference," said Xu Dianfang, an official with the Shanghai Education Commission. "Local primary schools are required to launch gender education among grade one and grade two students."

But the commission didn't specify any one textbook or detail the content that should be taught. Many schools design their own sex education curriculum and class materials.

The textbook is based on the sex education materials of the Primary School Affiliated to the University of Shanghai for Science and Technology.

Xu Jin, deputy principal of the school, said they found many parents fail to provide correct answers to students' questions of "Where do I come from?" So the school started sex education six years ago.

The book has been published by the Shanghai Education Publishing House, and 18 primary schools have chosen to adopt the textbook in a pilot program. The textbook is also available at bookstores.

However, some parents think the book is too revealing and fear that it could lead to the early onset of puberty.

"Grade one and two pupils are too young to learn this," said Gong Sidong, mother of a girl in grade three.

"I think they just need to learn about where the private parts are and they cannot touch others' private parts or let others touch," she said.

Zhou Haiwang, a researcher at Shanghai Academy of Social Sciences, hailed the sex education textbooks.

"More kids experience early puberty now," Zhou said. "Children also have easier access to sex information now."

He said the Shanghai version is appropriate because it explains the basic theory without going into details, while the Beijing version is too revealing.

"If schools teach the grade one students all the stuff, what are they going to teach the grade four and grade five students?" he asked.

He advised schools to implement progressive education on sex.