An anti-teen sonic device was criticised by watchdogs
British children are being "demonised" by a society that is locking too many of them up, according to watchdogs.
The joint report by children's commissioners for all parts of the UK said attitudes towards youngsters were hardening across the country.
The experts said crime committed by children had fallen between 2002 and 2006, but the numbers criminalised had gone up by just over a quarter.
Their conclusions are part of a United Nations review of standards in the UK.
The four commissioners were appointed in a move to ensure children's rights are more effectively recognised by policy-makers.
Their report will be presented to the United Nations Committee on the Rights of the Child.
In their document, the commissioners said most children were happy and that policy-makers were trying to improve the situation.
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They added that too many children were being put through the criminal justice system and the poverty experienced by one in three youngsters was unacceptable for a rich nation.
The experts said more children were scared in their neighbourhoods and, citing previous studies, drank more alcohol, had deteriorating mental health and felt more pressure at school than their European peers.
Public bodies are legally bound to put the best interests of a child first in decision-making. But the commissioners said this key legal safeguard had failed in some parts of the youth justice system for England and Wales.
"The system is dominated by a punitive approach and does not sufficiently distinguish between adult offenders and children who break the law," says the report.
"Compared to other European countries, England has a very low age of criminal responsibility and high numbers of children are locked up. Too many children are being criminalised and brought into the youth justice system at an increasingly young age."
The report attacks the use by some shop-keepers, businesses and local authorities of the Mosquito teen deterrent.
The device emits a high-pitched squeal which can generally only be heard by the under-25s.
While ministers had not endorsed Mosquito, the commissioners said they had also done nothing to ban technology which indiscriminately affected those within its range.
This over-use of custody absorbs vast resources which would be better spent on tackling the causes of these problems by preventive work in the community
Paul Cavadino, Nacro
Kathleen Marshall, Scotland's commissioner, said: "We have highlighted areas that remain a concern, including significant differences in juvenile justice in some parts of the UK and the public's attitudes towards children and young people.
She added: "We look forward to briefing the Committee in Geneva to outline the findings of our report and to work with the Committee to make sure we can help improve things for children and young people in a tangible, sustainable and meaningful way."
Responding to the report, Children's Minister Beverley Hughes said: "We are 100% committed to improving children's wellbeing. Over the course of this government more than 600,000 children have been lifted out of poverty, almost 3,000 children's centres have been built and school funding has been increased by 87%.
"However, we are not complacent. The fact that we created a new government department for children, schools and families shows how serious we are about helping families and communities to give their children a happy childhood.
"Our Children's Plan is our long-term vision to address many of the issues raised in the UNCRC report."
Paul Cavadino, chief executive of crime reduction charity Nacro, backed the suggestion that the youth justice system needlessly criminalises children.
"Every year we lock up thousands of young people with histories of physical and sexual abuse, parental neglect, family conflict, school exclusion, substance abuse and mental health problems," he said.
"This over-use of custody absorbs vast resources which would be better spent on tackling the causes of these problems by preventive work in the community."
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