Half a million school children in Britain are unhappy with their lives, according to a new study published today.
The Good Childhood Report 2012 found that one in 11 youngsters (9%) aged between eight and 15 have a low well-being at any given time.
It also revealed that unhappiness increases dramatically with age - more than tripling from the age of eight (4%) to the age of 15 (14%).
The Children's Society, which published the report, said children with low levels of happiness are much less likely to enjoy being at home with their family, feel safe when with their friends, like the way they look and feel positive about their future.
They are also more likely to be victimised, have eating disorders or be depressed, it said.
The study, launched today by The Archbishop of York Dr John Sentamu, saw experts analyse the interviews of more than 30,000 children aged eight to 15.
It found that family has the biggest impact on their happiness, with loving relationships between a child and their family 10 times more powerful than family structure in increasing well-being.
Researchers discovered that stability was also an important factor in young people's well-being, with children who experience a change in the people they live with twice as likely to be unhappy.
Almost a quarter (23%) of children who have moved home more than once in the past year also showed low levels of well-being.
Elsewhere, researchers found that children liked to be similar to their peers, with those who have a lot less, or even a lot more pocket money having lower levels of well-being.
Material factors were also of deep importance, according to the study, with children in families who have experienced a reduction in income more likely to have low well-being.
Youngsters also were three times more likely to be unhappy with their appearance if they did not have clothes to "fit in" with their peers, with the trend increasing in age and among girls.
Elaine Hindal, the society's childhood director, said: "We are calling for a radical new approach to childhood, placing their wellbeing at the heart of everything we do. Our research has exposed that how children feel really matters.
"We know that, right now, half a million children are unhappy. We have discovered the key reasons for this unhappiness and what we can do to make it better. We want our country to be the best place for our children to grow up. Yet unless we act now we risk becoming one of the worst and creating a lost future generation."
Dr Sentamu added: "The moral test for any society is how it treats its most vulnerable, including its children.
"The fact that at any one time half a million children are unhappy with their lives should be a wake-up call to us all."
The charity made a series of recommendations on how to improve the well-being of youngsters, identifying six "key priorities" that were essential for a happy childhood.
They include the right conditions for a child to learn and develop, positive relationships with their family and friends, a safe and suitable home environment and local area and the opportunities to take part in positive activities that help them thrive.
The charity also said children needed to have a positive view of themselves and a respect for their identity and enough of the items and experiences that matter to them to have a positive well-being.