A Prisons and Probation Ombudsman report into the 2011/12 deaths, found that opportunities to act on warning signs and minimise the risk of harm were missed in all three cases.
Ryan Clark, 17, who died in April 2011 after being found unconscious in his cell at Wetherby Young Offender Institution (YOI), was the first child to die in youth custody since 2007.
His death was followed in January last year with that of 15-year-old Alex Kelly at Cookham Wood YOI and 17-year-old Jake Hardy at Hindley YOI just a few days later – both apparent suicides.
The report by ombudsman Nigel Newcomen found that although the three were “extremely vulnerable”, they were all placed in YOIs rather than secure training centres (STCs), which have a higher staff-to-inmate ratio.
This was despite, in two of the cases, youth offending teams (YOTs) recommending placement in an STC.
The report also highlighted problems with information sharing and a “lack of shared understanding of vulnerability” between YOTs, court custody teams and YOIs.
And warning signs that the young people were at risk of self-harming were not acted on. One of the boys damaged his cell, but the incident was treated as a disciplinary issue rather than a sign of vulnerability.
Meanwhile, the system for monitoring and supporting those considered to be at risk of self-harm or suicide in custody, known as Assessment, Care in Custody, and Teamwork (ACCT), which two of the boys were subjected to, was found to be “insufficiently child centred”, failing to address the “complexities and special vulnerabilities” of children.
The report also raised concerns over staff training.
“One boy disclosed past sexual abuse to a member of staff (the first time he had spoken of this at the YOI),” the report said.
“While there was no criticism of the individual involved who appeared to have handled this to the best of their ability, it is a concern that prison officers who work with (often vulnerable) young people are not given training about how to handle such discussions.”
In total, the report made eight recommendations on placement; information sharing; assessing vulnerability; the ACCT process; treating mental health problems; addressing bullying; personal officers and sources of external support.
Frances Crook, chief executive of the Howard League for Penal Reform, said: “This important bulletin reveals the terrible consequences of putting these children in prisons, based on a system for adults, which puts punishment before welfare needs.
“The deaths of these three boys in custody in just one year might have been avoided if they had received a sentence outside the prison walls that focused on their needs. It is clear that lessons have not been learned.
"Previous investigations by the ombudsman into child deaths between 2004 and 2007 highlighted the impact of problems like bullying and mental health issues.
"This report shows that history is, as usual, repeating itself and it is time for change.”
Deborah Coles, co-director of the prison deaths charity Inquest, called for a wide-ranging inquiry to explore the issues raised.
“There is an urgent need to learn from the failings that cost all these children their lives," she said.
"The government needs to act. An independent, holistic inquiry, where these issues are examined in the context of the entire system of detention for children, is long overdue. It’s time to break the cycle of harm and death.”
John Drew, chief executive of the Youth Justice Board, said pending the outcome of inquests into the deaths, the organisation is reviewing all available information about deaths of children in custody and has begun to consider how best to ensure changes are made.
"Every death of a young person in custody is a tragedy and following any such death we seek to learn lessons, helping to improve all aspects of welfare and care.
"The cases referred to in the Prisons and Probation Ombudsman Bulletin are still awaiting inquests, which prevents us from providing any more detailed comment in respect of these."