Keyron McDermott shares with USA Today readers the disturbing story of his experience as a substitute teacher.

There was a small ruction in third period; the principal and I discussed it amicably, and I barely gave it second thought. However, a couple weeks later, I received a letter informing me he was removing me from the sub list! Explanation (from said letter): he “visited with the class,” and the “interactions between yourself and the students were not such as meet our expectations for substitutes.”

A parent reported that a student had videotaped me on his cell phone. So, no doubt if there were a hint of unethical practice — singling a child out for ridicule, touching anyone, or making unreasonable demands — either on the video or in student testimony, my infraction would have been fully detailed.

Nothing.

What students apparently objected to was me handing back their papers, hectoring them about language errors. I told them unapologetically, “This is your native language, people! Second grade mistakes — not distinguishing between ‘your’ and ‘you’re,’ misspelling ex(c)ercise, leaving off caps and periods — from freshmen and sophomores are unacceptable … “

So I wouldn’t be accused of making unreasonable demands, I wrote corrections on the board. All they had to do was copy them.

Why do the students make such elementary mistakes? Too much Common Core?