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Basic checks are not made when placing these "vulnerable and potentially dangerous" children into homes, the Inspectorate of Probation found.
It said sex attackers had been placed with abuse victims and one teenager was moved 31 times.
The Department for Education said plans were being developed to improve care.
The inspectorate, along with education watchdogs Ofsted and Estyn, examined the cases of 60 looked-after children in six regions who required supervision in order to stop them from committing crimes.
It found around a third of children were placed more than 100 miles away from home and nearly two-thirds were placed 50 miles away.
Regulations require local authorities to allow the child to live near their home, as far as reasonably practicable, the report said.
Distressing casesIn one example, a 16-year-old boy had been moved 31 times since coming into care at the age of three, including one placement which lasted less than 24 hours.
Inspectors said of the "most disappointing" findings was that some youth offending staff gave little thought about the emotional impact on children of being in care and what was needed to address their problems.
Chief inspector of probation Liz Calderbank said: "What we saw in this inspection really shocked us. The case histories were really quite distressing. You have to ask yourself - what kind of adults will they grow up to be?
Continue reading the main storyToo often, the state proves to be a poor parent as the tiny minority of children in care become the substantial number behind bars”End Quote Juliet Lyon Prison Reform Trust "We came across one girl who had 27 workers, and these were just the ones she could remember. All of of these things are impacting on their life chances, what we are seeing for these children are very poor outcomes.
"Many of them are growing up and then we fear drifting into the prison service or the mental health system."
The report said youth offending team staff and other agencies did not "always work effectively together in the best interests of the children".
In two-thirds of the cases, children were not being sufficiently protected due to poor planning and assessment.
A fifth of the children had themselves been a victim of crime while under supervision of the youth offending team and just over half the children inspected had offended within the care environment.
In one case a 13-year-old girl who was a victim of sexual exploitation was found having sex with a 15-year-old boy in the children's home. Sexual videos of her were later found on his mobile.
Ms Calderbank said youth offending team workers' aspirations for the children were "depressingly low". The report said many staff had become "desensitised" and are "under-qualified".
Care to custodyA Department for Education spokesman said it was "completely unacceptable" that some local authorities and homes were failing children.
"Children placed far from their homes are extremely vulnerable. It is essential that local authorities responsible for them provide the vital support they need to keep them safe and well and to encourage their potential. Where children are offenders, this will include working with Youth Offending services to prevent any re-offending," he said.
"Three expert groups are currently developing proposals to improve the care provided by children's homes. They are due to report back shortly and we will respond on the action we intend to take in the New Year."
Juliet Lyon, director of the Prison Reform Trust, said: "Let down by families and local authorities alike, with a trail of failed placements and further and further from home, far too many children find themselves on the dreary, damaging route from care to custody.
"Too often, the state proves to be a poor parent as the tiny minority of children in care become the substantial number behind bars."