I was born in 1950. The standard grammar books that my teachers used in junior high and high school maintained that the singular masculine pronoun (he, him, his) was masculine when it referred to a man ("John Smith signed his name on the form") but was the "common gender" when it didn't refer specifically to men or women ("Everyone on the bus brought his own lunch:). In other words, since "everyone" was singular, the pronoun had to be singular as well (as opposed to "their own lunch") and the choice of the ordinarily masculine pronoun wasn't inherently sexist--you had to pick "his" or "her" and why should women be used as the default?--or at least that's apparently the thinking behind the justification of using the singular masculine over the singular feminine.

As an English teacher, you're doubtlessly aware of the problem of what is inherently a choice that favors masculine power over feminine power. And the "progressive" grammar guidelines suggest moving everything to the "neutral" plural ("All the students on the bus brought their own lunch."--although the singular "lunch" isn't very logical).

But even this kludge ignores the fact that for generations, the masculine singular pronoun was considered "neutral."

So given the historical artificiality of pronoun usage, it seems odd to me that some sticklers have suddenly objected to "pronoun choice" as if there is some standard form that renders language gender-neutral.