There was a high school physics teacher who subscribed to a mail list I once belonged to. Everyone disliked him because he was an idiot and most of what he said was both ignorant and offensive.
He was nearly illiterate — a scary fact given that he was a teacher of our young people. When called to account for the poor quality of his posts he would excuse himself saying "I'm a physics major, not an English major." But how much do you have to know to be aware that you don't end a sentence with a space followed by a period followed by the first letter of the next sentence with no space before it? Or that sentences are begun with the first word capitalized, not the second? Has he never noticed that's how it's done in any book he's ever read?
Maybe I don't want to know the answer to that question. It's likely he's never read a book since the last one required of him in his school days, or much of anything else for that matter. I'm impelled to wonder how much he knows about physics.
As for not being an English major — English is his only language. I'm not a domestic chores major, but I do know how to bathe myself, brush my teeth, get dressed, and tie my shoes. There is a certain minimum standard that even most mentally challenged persons are expected to achieve. And for a high school teacher, regardless of his subject, I would expect and insist on a standard of communication skill well above the norm for untrained society.