Praise My Failing Grade

The F I got the other day
    I put it in my pocket.
         I did not stress about that test
             It seemed I just forgot it.
Math is not my subject
    And our substitute a curse.
        I'm sorry to be sour,
            But that Sub was just the worst.
If he taught us the product rule,
    And recalled a proof or two,
       Then maybe this poor math grade would
           miraculously improve.
I know- I should have studied more,
    And blah blah blah I'm dumb.
       But this is just one measly test
            Don't say I'm just a bum.
Since when did tests reflect our skill
   Determine our IQ?
       Choose other ways to test our knowledge-
           you'll see we're smart, its true!
The F I got the other day
      I won't give another thought.
           it simply shows we didn't learn
                   And our subs an idiot.