@HS Up at the pearly gates St M checks your latest tax return, takes away your credit cards and passes you on to St P, who checks your grammar, so PP should be okay; unless of course St P has gone fishing.

@WW I just use plain SV[OPT} 95% of the time. Romance and Germanic languages are usually Time-Manner-Place TMP as opposed to English often MPT, and VO unsplittable.
Slav languages tend to put old info first, new info last. Verb comes at the end in Korean
and uses post-positions and no separate relative clauses so that's why we need to addess word order:
(In English) I go to the shops in-order -to buy bread
(in Korean) I (optional) bread buy - in-order to shops to go

The Konglish for this sentence in Korean would be na-do ppang sa-ro kayo (I-do bread buy-in order-to go).
Horses for courses.

@WW all a bit too academic for me; in teaching I just use SV[OPT] to represent a clause, as in "Although SV[OPT], SV[OPT]."; and with add-ins as needed like:
QxSV[OPT]? or SVOMPT or SxMpp[OPT] - for "She had quickly walked her dog down the street the night before." where P=place T=time x=auxiliary M=manner Q=question-word. Indeed I pronounce it "svopt" so sts remember it, so I don't need to explain or use "clause".
It is my Vergeltungswaffe.

English has been described as a residual verb-comes-second (V2) tongue. Thus we can say:
a. Most sought are upper-income people, who tend to keep large balances wth the bank. (from Birner 1995: 239)
b. They have a great big tank in the kitchen, and in the tank are sitting all of these pots
. (from Birner 1995: 241).

Using neither (in front of the first verb) .... nor , usually triggers a V2 structure.

If one wishes to teach "grammar" a little more directly, one can set a task like:
"A friend of mine says there are thirteen meaningful ways to join together the two sentences "Roses are red' and 'Violets are blue' : what are they and explain the differences in nuance". Good practical stuff not boring analysis and terminology.

Often one does not need to teach grammar as such; just select a befitting topic to elicit it. For instance, to elicit "third" conditionals, topics like:-
"What effect did the British occupation have on India?"
"How has the Japanese occupation influence Korean education since WWII?"
or more directly:
"If the USA had successfully supported Chiang Dae Shur (ie chang kai shek) and the GuoMingTang, how would China be different today?"
It's not about learn grammar per se, it's about being able to use it.

@WW no offence intended, Geordie or Glaswegian both incomprehensible to me, but good English nevertheless.
In truth one's the grammar of one's natural English dialect is the one that makes most sense. If one is north-country saying "we was" and "she were", that's your natural grammar, and "standard" Englsh grammar is something you learn at school for writing.
However, ESOL is a different kettle of fish. For many ESOL students present perfect is a strange concept, just as the "definite/indefinite" conjugation in Hungarian is for me, and no amount of grammar exercises can make it automatic.
Again, in Korea (and Japan) they learn English grammar, grammar, grammar at school with very little practical result.
Equally in my experience, most students who reach an advanced level have worked through something like Murphy; and equally just working through Murphy does not per se make a student advanced: so grammar, grammar, grammar alone is not enough. I guess you know that already. Perhaps the real point is that it is quite rare for a Mandarin, Cantonese, Vietnamese, Thai or Korean speaker to get to a CAE level. The gulf in concepts is just so wide. Ban Ki Moon is exceptional - Korean has tenses and so on but lacks "f", "v" and has the l/r issue and is SOV, and like Slav tongues lacks articles; moreover (as in Hungarian) generalizations are made in the singular even for countable nouns. It is the same for us trying to learn a tonal language like Thai, Vietnamese, Mandarin, or Cantonese. The gulf is huge.

De grammaticae eruditione: The first thing we would need to establish is what is the purpose of learning grammar; what are the aims, goals, and objectives? We can hardly determine this without discussing exactly who is doing the learning and why they need to, and what they need.
I would suggest that those least of all in need are native speakers - group one. There are some perhaps whose at home dialect (perhaps deeply Scottish or AAVE) is so far removed from what is the acceptable norm in business and at university that some work toward more standard writing is needed - group two. And my third group would be those who speak very little English at home - it is a second language. This would apply to perhaps 200 million "English speakers" in India and other erstwhile colonies including USA where my understanding is that perhaps a third of the pop is Hispanic speaking at home.
Plainly the first group (who already speak RP etc) have little need beyond punctuation. The second group may need more work. The third group and the rest of the world plainly need grammar as a crutch to get the word order, tenses and so on right. Even so I avoid grammar terminology as much as possible, as the purpose is to put together good English not to know the difference between a "voice" and a "mood", or indeed "indicative","imperative", subjunctive, optative, and all the other moods, unless that terminology is sine qua non for understanding. For example they don't need to know that "ago" is a postposition not a preposition, just put it after the noun not before.
That said, some grammar terminology is needed: Subject, Verb, Object, Past Present Future, Modal, auxiliary, Continuous - I have to teach them all, as they are all in the books and I need them anyway. One needs to remember that in languages such as Mandarin there are no tenses so they cannot learn them at school and have no awareness.
As to the usefulness of Latin grammar, well consider the sentence: I was given the book.
English is a quirky language and somehow we manage to have an object in a passive sentence, which is absolutely impossible in Latin and indeed other European languages. So how does Latin grammar help here? Again Slav languages do not have a past perfect, nor do they distinguish praeteritum irrealis and futurum irrealis. Should they learn latin grammar first or just get on with English?
Incidentally modals in English are, in terms of word roots, already a preterite - that is why there is no final 's', why 'must' is seemingly inconjugable.
What all this means is that there are no cast-iron grammar rules chiselled in stone. The whole thing is but a crutch, means to an end, and whatever means is justified if the end output is normal acceptable English. So in this case "was" or "were" or whatever will do.

If you look on wikipedia possessive apostrophe it gives the historical background and says that the convention did not become established until the nineteenth yearhundred.
What I think is happening these days is that people can't be bothered to find the punctuation on the keyboard, so apostrophes and commas are withering away.
I am not at all sure I would bother myself, esp for the plural possessive. Quite what I would do if I were writing formally by hand - well who does that these days outside an Enlgish Exam. I would hope that IELTS examiners would not get all picky about it as the meaning is usually quite clear and unambiguous, and there are far more weighty criteria to consider. On the other hand I might expect a proof-reader to correct it as per style guide. Basically dying yet not by any means dead yet IMHO.

timor tui incomprehensionis ironiae meae conturbat me