A report into the youngest person to die in custody has called for sweeping changes to how children are dealt with in the youth justice system.
Staff had earlier subdued the 14-year-old with a legally-sanctioned special physical blow to his nose.
An official report said it was unacceptable to detain children except in exceptional circumstances.
Adam Rickwood was sent to the Hassockfield STC in County Durham in July 2004 after being charged with an offence of wounding.
He was found hanged by his shoelaces in his room four weeks later. An inquest jury returned a verdict of suicide after a month-long hearing into the circumstances surrounding the use of restraint techniques.
During the inquest, the jury heard that the teenager had suffered a string of mental health problems including suicidal tendencies alongside drink and drug abuse.
He had written to his mother warning he would kill himself if forced to stay in the unit.
Hours before his death, staff had ordered the teenager to his room after he and other boys became rowdy.
Staff told the inquest into his death that the boy began a confrontation and refused to calm down. As an attempt was made to restrain him, he lashed out and attempted to bite.
One member of staff restrained the boy with the "nose distraction technique" - an upward blow to the nose.
The technique is a legally sanctioned method of subduing a teenage detainee in extreme circumstances and is designed to shock and stun.
The Howard League for Penal Reform has alternatively described it as blow with the outside of the hand rather than a punch with a closed fist.
The 14-year-old had a nose bleed following the blow and was carried to his room face down to prevent him choking on his own blood.
Gill Rigg, chairwoman of the Lancashire Safeguarding Children Board (LSCB), the official body charged with investigating what happened, said children under 16 should not be kept in custody in all but the most exceptional circumstances.
But the body also wanted the government to provide "urgent clarification" on the legal status of children placed by courts in secure centres.
Children remanded by court order to these centres are classed as "looked after" children, a status which triggers oversight obligations on social services departments. However, not all children subject to detention are monitored in the same way.
The report also called for a review of child custody restraint techniques.
The Ministry of Justice announced such a review in July, telling Parliament that a panel would look into all the issues surrounding their use.
One of the most controversial, a form of hold, was banned following the death of another teenager in custody.
The report also said children under the age of 16 should be held in a secure unit within 50 miles of their home and that the receiving unit should be given a full history of the child's mental health.
A spokesman for the Youth Justice Board said it was looking at the report with interest.
"Everything possible should be done to keep young people out of custody," said a YJB statement.
"However, we need the full commitment and input of children's and other mainstream service providers to ensure that appropriate early interventions are made to keep those children and young people identified as at risk of offending out of trouble in the first place, and to ensure their needs in and following a period in secure accommodation are met."