从思想到行为有违法犯罪倾向的少年juvenile delinquent

• 这些学童滞留在外，往往变成一群特异的问题少年。

  These school children that are excluded in detention often become juvenile delinquents.

• 从前他是个问题少年，打群架，到处惹祸。

  He was once a juvenile delinquent, always fighting and getting into trouble everywhere.