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。

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。

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。

He used to be a "problem child".

他曾经是一个问题小孩。

To study the significance diagnosing problem child with neuropsychological test.

探讨神经心理测试对问题儿童的诊断意义。