Un-fair is Foul

My English teacher, Mr. William Hays,
However wise and witty he may be,
Is, to my eyes, a man of unfair ways.
For he grades my work no higher than a C.
But still I try, though why I do not know,
To write a paper he would deem sublime,
But still my grades much lower seem to go
Until I wonder why I waste the time.
If, in my favour, his dispose would lean,
I'd be less hurt and less inclined to blame,
My grades on his unfair and vague routine
Though nonetheless, unfair he'd be the same.
Yet still, I'd have less hate toward Mr. Hays,
If but from time to time he'd grant me A's.