Conjugations: English as a Difficult Language

I know, you know, he knows.
I come from a class where some know,
some will know, and others will never know.
But for the moment we know
that they must practice what they know
so that when they speak others will know
what they are saying with no
misunderstanding, no
need for interpreters, and they will know
this language their children already know. 

We move on to what we believe but cannot know
and we say, “Only God knows.”
But how do we explain, when someone wants to know
the difference between “Only God knows”
and “God only knows!”?