The Children's Society's Good Childhood Report said there was a period of rising well-being in children's happiness and satisfaction from 1994-2008, but this stalled and appeared to decline in recent years.
Officials at the Children's Society warned the public should not dismiss the drop in well-being in the early teens -- teenagers age 14-15 have the lowest life satisfaction -- as a normal and inevitable part of growing up.
Britons ages 14-15 were less likely to be happy about school, their appearance and the amount of choice and freedom they have, than the others surveyed, the report said.
The charity, which questioned 42,000 8-17-year-olds, said all of society has a part to play in boosting children's well-being.
"The well-being of our future generation in Britain is critical. So it is incredibly worrying that any improvements this country has seen in children's well-being over the last two decades appear to have stalled," Matthew Reed, chief executive of The Children's Society, said in a statement.
"These startling findings show that we should be paying particular attention to improving the happiness of this country's teenagers. These findings clearly show that we can't simply dismiss their low well-being as inevitable 'teen grumpiness.' They are facing very real problems we can all work to solve, such as not feeling safe at home, being exposed to family conflict or being bullied."