He added that £245 million a year is spent on detaining 16,000 offenders, who need to be educated whilst in detention, to use the time "sensibly".
Secure colleges are to be considered in a bid to improve the education received by young offenders.
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Accompanied by the Duke of Edinburgh, the Queen will attend the opening ceremony of the fifth session in the Holyrood chamber.
Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
The former shadow work and pensions secretary is considered a more viable candidate than Angela Eagle, a Labour source has told ITV News.