as good as gold 很乖的；很可靠的；（小孩）规规矩矩的

【例句】
The boys were as good as gold on our walk.
我们散步的时候，这帮小男孩表现得很乖。

The children caused no trouble all day; they were as good as gold.
一整天孩子没惹过一点麻烦，他们乖极了。