Oeco’s post and some in the other thread imply that teaching about grammar is about teaching a fixed set of grammatical rules: about telling people not to split infinitives and so forth.
To my mind, it is about giving someone the skills to analyse what role is played by different words and clauses within a sentence. I don’t think it should require an enormous amount of time each year, perhaps an hour a week for one term per year or something like that. I would hope that by the time they leave school, the students can identify the various tenses, moods, cases and parts of speech. If they choose to write using non-standard forms, so be it, but they should be able to look at what they’ve written and understand on a grammatical level what they’ve created.
Without this knowledge, their ability to discuss language will be incomplete. People will tell them things about what they’ve written and they just won’t understand.
I’m not in The Humanities at all but people do ask me to check their writing, for some reason. My cousin is going to be a primary school teacher, and last year she sent me a few pages of text to proofread. The target audience was her professor, I suppose, and it may well be that she has a good idea of his standards, but I made some corrections and simple suggestions to make it more appropriate for a formal presentation. There were broad structural problems, and the conclusion just petered out, but she understood these criticisms. She didn’t know what I meant by “Be careful with number agreement,” and “dangling modifier makes sentence ambiguous”. After I went through some examples with her, she still didn’t seem to get what I was saying. A bit more probing has told me that she doesn’t reliably know what a verb is: she was aware it was a “doing word” but considered that this would include words such “action"*.
You might say that if I kept on correcting the number agreement in her screeds for a few months that she would, by osmosis, pick it up without having to know what a verb is or what the phrase “number agreement” means. Given that she has been in the education system for some fifteen years now, I think she probably won’t: I think we can say that we tried that, and it didn’t work, at least in this case. If she had done just a little grammar, not a barrage or a whole course or anything like that, it would be easier for me to help her in this.
Maybe she’d still be making mistakes through inattention, but at least she’d see what I was getting at, and there’d be some hope of improvement. Next year she will be teaching English to children and this is one area she won’t be able to help them with.
I’m sure that you’ll be able to find non-standard grammar in this post. You’ll find what are universally regarded as errors. When you tell me about them, at least I’ll have some idea what the fuck you’re talking about.
It’s not the be all and end all. It won’t make someone a good writer. It won’t teach someone how to be witty, or how to structure a paragraph well. It won’t make me a sandwich. There are millions of things it won’t do. What it will do is empower someone to make more informed decisions about their own work, in this one particular limited aspect of language. It won’t benefit everyone, as different people learn in different ways, but it will benefit some. Mas vale algo que nada.
Very generally, I favour an informed populace. Not everyone needs to be Isaac Newton but everyone should have at least a smidgeon of science knowledge: some rudimentary grasp of the facts of the large processes at play in the physical world, and some kind of understanding of what science is. You don’t need to be Ben Bernanke but you should know in broad strokes what is happening in the economy. In a democracy, and to some extent even out of one, responsibility lies with “the people” that once lay only with monarchs. Everyone requires detailed knowledge pertaining to their particular profession, but each citizen should also be a generalist. Language is one of humanity’s most important tools, and it follows that each of us should know at least a sliver of linguistics. How could one give a general coverage of linguistics without touching on grammar?
*Yes, I am aware that action can be a verb. You may safely assume that I mean she considered it would include words such as “action” in cases where the context makes it clear it is a noun.
EDIT: removed the words “to have” before the words “some rudimentary grasp”