Figures released in parliament show there were just 119 GCSE passes in public sector young offender institutions in 2010/11, the latest year for which figures are available.
That is a 49 per cent drop on the number of passes for 2009/10, when the figure stood at 232.
Although there has been a decline in the number of young people in custody – the decline in GCSE passes is far steeper.
Youth Justice Board figures show the average number of 15- to 17-year-olds in custody for the period fell from 2,285 in 2009/10 to 1,941 in 2010/11 – a drop of 15 per cent.
Frances Crook, chief executive of the Howard League for Penal Reform, described the fall in GCSE passes as “very concerning”.
Young offender institutions are required to provide at least 15 hours of education a week.
“Children in prisons have been excluded from mainstream services and are forced to remain in cells for long periods with access to only the most basic education,” Crook said.
“If they are receiving just three hours’ teaching a day, is it any wonder that only a small number of them are leaving custody with the building blocks for the future?
“These figures only add to the compelling evidence that these warehouse-like establishments fail vulnerable children and fail the public.”
Education provision for young offenders has been subject to a number of proposed changes in recent years.
Responsibility for young offender education was due to be handed to local authorities in September 2010. But this was delayed by the coalition government.
As such, contracts for young offender education are still being commissioned on a national basis.
The Ministry of Justice has been contacted for comment.