SHANGHAI, China — A teenager’s suicide after being barred from a key high school exam for not tying back her hair underscores the intense pressure on millions of Chinese who began taking annual college entrance tests Wednesday.

Worries are rising about academic stress. There are 2.6 million places at China’s universities, but the competition is fierce — 9.5 million youths are taking the three-day exams that are widely viewed as crucial to career and financial success.

Although 16-year-old Wu Wenwen’s suicide occurred in January, during high school end-of-term tests, it is resonating during this week’s college exams.

According to her family and newspaper accounts, Wenwen drowned herself after she was stopped at the exam room door because her hair wasn’t tied back as her school required.

She returned in barrettes, but was told the exam had started and she was too late to take it. Wenwen phoned her mother in tears, and then disappeared. Her body was found that night in a nearby lake.

As in Japan and South Korea, schooling in China has become a nail-bitingly stressful ordeal for children and parents alike, one that experts say causes undue emotional distress.

‘‘Pressure from study and exams is a top reason for psychological problems among Chinese youth,’’ said Jin Wuguan, director of the Youth Psychological Counseling Center at Shanghai’s Ruijin Hospital.

In China’s increasingly success-oriented cities, academic stress is seen as a rising cause of youth suicides and even murders of parents by children unhinged by overwhelming pressure to perform.

China doesn’t keep comprehensive statistics on student suicides, but Jin said health care professionals see the problem worsening, even among elementary students.

Most Chinese schools still lack counselors and teachers receive little training in spotting emotional distress, Jin said. Parents are little help, often piling on pressure while ignoring their children’s emotional development, he said.

‘‘It’s a basic unwillingness or inability to recognize and deal with emotional problems,’’ Jin said.