In one year she turned from a problem child into a model student.

一年内，她从问题儿童变成了模范学生。

《牛津词典》

Thanks to my English teacher, I turned from a problem child into a model student in just one year.

多亏了我的英语老师，我在一年内从问题儿童变成了模范学生。

youdao

She was a problem child , always in trouble with the police.

她曾是个问题儿童，总是给警察惹麻烦。

《牛津词典》

Often parents don't realize there's a problem because their child does not look fat.

VOA: standard.2010.03.09

And the problem for Freud is premature weaning of a child.

在弗洛伊德看来,问题就出在孩子过早断奶上面。

耶鲁公开课 - 心理学导论课程节选

Sheen has a long history as a problem child and I am not defending either his self-destructive or violent behavior.

FORBES: Charlie Sheen And Public Company Disclosure

You don't want to be seen as a problem child.

FORBES: Magazine Article

The Royal College of Paediatrics and Child Health said obesity was primarily a public health problem not a child protection issue.

BBC: Parental failure over child obesity is 'neglect'