Children in England are among the unhappiest in the world, behind countries such as Ethiopia, Algeria and Romania, research suggests.
The Children's Society report, which looked at 15 diverse countries, ranked England 14th for life satisfaction of its young people, ahead of South Korea.
More than a third of English children said they had been bullied in school, and half had felt excluded, it found.
The Children's Society called for a new law to provide counselling in schools.
Ministers said schools were encouraged to have counsellors available and all schools must have measures in place to tackle bullying.
The University of York carried out the research in England, which was then drawn together for the Children's Worlds project and compared with data from 14 other countries.
Researchers surveyed more than 53,000 children in total in 2013-14, aged between eight and 12, from diverse cultures and places, from remote villages to large cities.
Levels of satisfaction with "life as a whole" were highest in Romania, where the mean level of satisfaction among 12-year-olds was 9.5 out of 10, followed by Colombia with 9.3 out of 10.
England came 14th out of the countries surveyed, with 12-year-olds giving a mean satisfaction score of 8.4 out of 10, and 7.1% reporting low levels of well-being and happiness.
The survey also found that levels of unhappiness at schools in England grew as children got older - 61% of 10-year-olds said they enjoyed school but the figure fell to 43% by the age of 12.
English children were the most likely of all the countries surveyed to say that they had been left out by other children in their class at least once in the last month, the survey found.
More than a third (38%) aged between 10 and 12 reported being physically bullied in the previous month.
English girls ranked second lowest for happiness with their body confidence, self-confidence and appearance, rating their satisfaction as 7.3 out of 10 on average. This places them just above South Korea, with a mean score of 7.1.
Colombian girls topped the table for body confidence, with an average rating of 9.6, followed by Romania with 9.4.
Whilst the findings do not indicate why children in England feel more unhappy than others, Kevin Courtney, deputy general secretary of the National Union of Teachers blamed poor mental health on the "narrow curriculum" and "exam factories" culture in schools.
He said children were too often branded "failures" when barely into primary education, and tests at all stages of school life could lead to "serious stress-related anxiety."
Children's Society chief executive Matthew Reed said it was important for schools in England to make counselling available for all children.
"It's already available in Wales, it's already in Northern Ireland - a legal responsibility for schools so all children do get the support they need," he added.
The charity also called for an increase in funding on children's mental health.
A Department for Education spokeswoman said the government was working hard to tackle the issue of mental health, and was providing more than £7m to help schools tackle bullying.
"We are also promoting greater use of counselling in schools, improving teaching about mental health, and supporting joint working between mental health services and schools," she said.