Kenny was 21 when he learned how to read and write.
His education stopped at the age of 14 when, while living in care, he was sent to a young offender institution for a year for stealing cars.
Now 28 and living in Middlesbrough, Kenny said he was visited by a social worker during his time in custody, but was not offered any education. He spent much of his time in the punishment block, in solitary confinement.
"You're in there 24 hours a day, and you can't even see out of the window," he said.
"There was nothing to do. If they had given me some work, I might have done it just to pass the time."
Kenny is now planning to work as a mentor for the charity, Nacro, which specialises in the care and resettlement of offenders.
The devastating impact of custody on the education of looked-after children was highlighted in a report by the National Children's Bureau last month.
It found that children from care were given little if any support either when in custody or immediately after their release.
Of the dozen 15 to 18-year-olds featured in the study, seven had reoffended within three months of their release. None had received any education or gained a job in that time.
Most of the teenagers in the study were taken into care between the ages of 10 and 14. Overall, an estimated 46 per cent of young offenders in custody have spent some time in care.
Di Hart, principal officer at the NCB's children in care unit, said:
"Without adequate planning and support these young people have few positive options for the future and are much more likely to re-offend.
"The picture that emerges from our study is one of fragmented planning, and poor outcomes. Young people often feel abandoned by the social workers they have come to rely on, and practitioners are confused over their respective responsibilities."
When Kenny was released from the young offenders institution in County Durham, at the age of 15, he received little help in getting his life back on track.
"I did have a social worker, but he was not bothered because I was doing his head in. He was forever coming down to the police station. He wanted to get rid of me.
"They kept passing me on from one person to the next. If they had tried harder, I might have changed and done something with my life."
Kenny said that although the system had changed slightly since he was a teenager, he sees his story repeated in the lives of many young people growing up now.
"There's a 14-year-old in my street who is totally out of control," Kenny said. "He's running round the streets all the time, drinking alcopops and smoking joints.
"I look at him, and see myself."
The NCB report, Tell Them Not to Forget About Us is available from www.ncb.org.uk