Asked to rate their satisfaction with life on a scale of 0 to 10, some 370,000 15-year-olds gave a mean score of 7.3, the Paris-based group said.
The respondents were among 540,000 from 72 countries that took part in a larger survey conducted by the OECD's Programme for International Students Assessment (PISA) in 2015.
The survey found great disparities between countries, with fewer than four percent of students in the Netherlands saying they were "not satisfied" with life, a figure that rises to more than 20 percent in South Korea and Turkey.
However the gap is minimal between high- and low- achieving students.
Bullying is "perhaps the most distressing threat to students' well-being," according to the study, which asked students how they felt about their achievement at school, their relationships with peers and professors, their home life and their leisure activities.
In 34 of the countries studied, more than 10 per cent of the students said their classmates make fun of them several times a month.
Among those who reported frequent harassment, 42 per cent said they felt like outsiders at school.
The study also warned about excessive internet use, saying more than one in four (26 percent) of respondents spent more than six hours a day connected at the weekend, and 16 percent said they devoted similar chunks of time online on weekdays.
"These 'extreme internet users' are more likely to feel lonely at school, have low expectations of further education, and tend to arrive late for school," the report said.
Sources of stress include anxiety about schoolwork and income inequality.
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