"I'm afraid I will soon be like Li Yu," Cheng said, sobbing. Li Yu is a student Cheng read about in a magazine article. She is an only child, five years older than Cheng. As Yu spoke to a Beijing Review reporter, her expression was featureless. She said she was relaxing the nerves and muscles in her face.

While riding the bus back home after school, Yu said she is accustomed to looking out the window, which she feels is her only exposure to the outdoors. She stays indoors most of the time--at home, in the classroom or in the house of her tutors. Yu began to learn the piano when she was not yet a primary school student. While in primary school, she attended the Olympic Math training course and English training course. Now she is in the first grade of junior middle school, and each week she has to attend three make-up lessons after school. "During this year's Spring Festival holiday, my parents let me rest for only a few days. I spent the other time studying, studying and studying," Yu said.

Every day, Yu travels a half-hour by bus to school. Actually there is a middle school only a three-minute walk from her home, but her parents sought help from an influential person to allow her to attend her present school, which is considered of higher quality as many of its students enter key senior middle schools.

Yu's parents once had the idea of renting a house near her school, but she refused. "I said to them it's not necessary to spend the money and effort, but in fact I had my own consideration," Yu said. The real reason was that she wanted to snatch a bit of leisure time from her busy life. "It's the only period in the day that I can take a breather and relax. I don't feel as relaxed even when I'm sleeping," she said. Yu often studies at night, staying up to 2 a.m. "Sometimes I sleep lightly and will suddenly wake up, feeling that I have an unfinished assignment," she added.

Cheng said he has had a similar dream several times: He finally finishes his college entrance examination, but the students are informed that something is wrong with the examination paper and they must take another exam.

He said he has the same feelings as Yu, as he also likes the atmosphere at night. "It's quiet and lonesome at night, which is closer to the state of my mind and I feel comfortable," he said, adding that he feels this kind of mood has become one of his characteristics.

Things that make him unhappy may not happen every day, but he cannot find reasons to be happy.

In China, there are many children like Cen Cheng and Li Yu, who are unable to enjoy childhood. The pressure they face is apt to lead to psychological disorders and even social problems, experts say.

Last September, the China Youth and Children Research Center conducted a survey on the lives of primary and middle school students in Beijing, Shanghai, Guangdong, Yunnan, Gansu and Henan. The survey showed that whether on weekdays or weekends, the study time of primary and middle school students is 50 percent longer than the guideline set by education departments. The time primary school students spent on homework on weekends in 2005 exceeded the guideline by more than 70 percent. Nearly half of the students surveyed attended make-up lessons over the summer holiday last year, and 57.6 percent of the students say they are in agony due to the heavy pressure of study.

"Among the children and teenagers under 17 in China, there are at least 30 million who suffer from all kinds of emotional disorders," said Wang Yufeng, professor at the Institute of Mental Health of Peking University. Of this total, the rate of mental disorders among primary and middle school students is 21-32 percent.

This large group can be divided into three segments. The first group consists of those suffering from schizophrenia or paranoia, which only accounts for a small part of the total. The second refers to those with such problems as attention deficit disorder, depression, autism and anxiety. Many children even suffer from bipolar disorder, which is considered an adult illness. The third group consists of those who are considered to be at high risk of developing a mental illness. That is, they have not been diagnosed with a mental disorder but they exhibit some symptoms, which will develop into an illness if not treated.

"What we should attach importance to is that children are suffering from attention deficit disorder, anxiety and depression at a younger and younger age," said He Xiaopeng, a journalist who focuses on childhood mental illness.

What makes experts particularly concerned is that the children are in an important period of character building. Their problems will have a direct influence on their personalities, causing inhibitions or emotional trauma and impeding the development of sociability, which will continue even after they grow up.

"It's like a person suffering from rickets due to a lack of calcium in his childhood. That can't be rectified after he has grown up, even if calcium is supplied, because the crucial [development] period has passed," said Zheng of the Beijing Mental Health Center for Juveniles and Children.

Actually, psychological problems among children have become relatively common in the world. According to data from the United Nations Children's Fund, the rate of mental disorders among children is 20 percent worldwide, meaning that one of every five children suffers from a psychological problem.

Dr. Liu Jin, a Ph.D. from the Center of Mental Health under the Chinese Center for Disease Control and Prevention, said, "It's the most conservative estimate that there are only 30 million children in China suffering from various mental problems. This figure has been used for many years and it's just an estimate. Now the number may reach 50 million." She further pointed out that China has never conducted a nationwide survey and that the figures are estimates based on local surveys.

Last year, an investigation by the Shanghai Women's Federation found that the mental disorder rate among primary and middle school students in Shanghai was 21-32 percent.

Since 1984, the Institute of Mental Health of Peking University has conducted four surveys of mental and behavioral problems among primary school students in some districts of Beijing. The percentage of those suffering from such problems was 8.3 percent in 1984, 10.9 percent in 1993, 13.4 percent in 1998 and 18.2 percent in 2001. Although the districts it selected were different each time, the situation appears to be becoming more and more serious.