汉译英：不怕小孩子笨，就怕他不用功.

按中文‘不怕....就怕’的表达方式可以这么说：

I am not concerned about the child's intelligence, what really worries me is his laziness.

但是老外有他们自己的表达方式：

The kid’s intelligence does not really matter,but his diligence does.

不怕....就怕 - not afraid that .... but afraid that ...

i am not afraid that the child is stupid, but afraid that he is not hardworking

你好！
这个表达我没什么固定的句型可以提供
对于你上面说的翻译 我提供~
There is nothing serious if he were lazy than stupid.
好像不是很工整..
不介意可以用的哦
谢谢

I'm not afraid of the kid's foolishness,I'm afraid that he isn't hard- working.
(My level is limited,only for reference.)

I don't afraid of foolish child,but of a lazy one.

用 not ... but ...

be afraid of - 有点不准确
不怕...就拍 没有固定的表达方式，需要根据句子灵活翻译。
我会翻译成：I am more concerned about a lazy child than a foolish one.