Confusing English!

I've been teaching English as a second language to a girl in the class I TA for. It's been so hard to teach her grammar, because English has a nasty way of establishing a rule and then promptly giving a bunch of exceptions. So when I found this little poem in my Adventure of English textbook, I thought it quite appropriate:

We'll begin with a box and the plural is boxes.
But the plural of ox should be oxen not oxes.
Then one fowl is goose, but two are called geese.
Yet the plural of mouse should never be meese.
You may find a lone mouse or a whole lot of mice.
But the plural of house is houses not hice.
If the plural of man is always called men,
Why shouldn't the plural of pan be called pen?
The cow in a plural may be cows or kine,
But the plural of vow is vows and not vine.
And I speak of foot and you show me your feet,
But I give you a boot...would a pair be called beet?...
The masuline pronouns are he, his, and him
But imagine the feminine she, shis, and shim!
So our English, I think you'll agree
Is the trickiest language you ever did see.