Young offender

A young offender is a young person who has been convicted or cautioned for a criminal offense. Criminal justice systems often deal with young offenders differently from adult offenders, but different countries apply the term "young offender" to different age groups depending on the age of criminal responsibility in that country.
United Kingdom.
The United Kingdom has three separate and distinct criminal justice systems: England and Wales, Northern Ireland, and Scotland. Young offenders are often dealt with by the Youth Offending Team. There is concern young adult offenders are not getting the support they need to help them avoid reoffending.
In England and Wales the age of criminal responsibility is set at 10. Young offenders aged 10 to 17 (i.e. up to their 18th birthday) are classed as a juvenile offender. Between the ages of 18 and 20 (i.e. up to their 21st birthday) they are classed as young offenders. Offenders aged 21 and over are known as adult offenders. 
In Scotland the age of criminal responsibility was formerly set at 8, one of the lowest ages of criminal responsibility in Europe. It has since been raised to 12 by the Criminal Justice and Licensing (Scotland) Act 2010, which received Royal Assent on 6 August 2010.
In Northern Ireland the age of criminal responsibility is 10.
Northern Europe.
In Sweden, the age of criminal responsibility is set at 15 since 1902.
United States.
In the United States, the age of criminal responsibility for federal crimes is set at 11. While this has been set at the federal level, each state is responsible for setting their own age of criminal responsibility. Thirty-three states have no minimum age for criminal responsibility, while the remaining 17 do. North Carolina has the lowest responsibility age of 7 years old and Wisconsin has the highest of 10 years old.
There are 1.5 million cases per year in the US that handle status offenses or criminal offenses by young offenders. However, only 52 juveniles were fully sentenced to prison-time between 2010-2015. Recidivism is common among young offenders, with 67% becoming repeat offenders.
Brazil.
In Brazil, the age of criminal responsibility is set at the age of 18. Anyone that is found guilty of committing crimes prior to the age of 18 is treated to other options rather than jail. These include, for children under 12, foster care options in order to get them a safer family, and, for young offenders over 12, being sentenced to complying with a range of socioeducative measures that can go from a warning to communitary work and even to internment in specialized facilities, which include basic schooling and profissionalizing courses that aim at preventing the offenders from resorting to crime to support themselves, although conditions in such facilities are often subpar. With a spike in crime rates among young offenders occurring in 2015, along with an almost 40% increase in internments of young offenders, there was a push to lower the age of criminal responsibility to 16, which ultimately failed.