I read CPL Vic's Post about Grading. And the funniest, most accurate, comment I ever got from a Teacher, actually came from my own Daughter. I was in Grad School, she was twelve. She already had a command of the English Language, Writing and Grammar beyond her years. And way ahead of skills.
So I had to write a 50 page Paper, and I had her Edit it. Not only was there enough red ink to make it look like the paper was wounded. I had to look up a lot of the "Copy Editing shorthand" notation marks.
At the end of the Paper she wrote this little assessment:
"Dad,
1) There are rules for Grammar. And a reason.
2) Punctuation is not an option.
3) You can't just sprinkle comma's and hope they work for the sentence.
4) Are you sure English is your First Language?

I made all the corrections she recommended.

I still do.