It is a matter of discussion among teachers whether or not we teach the past subjunctive, and my opinion is no more valuable than anybody else's on that subject. But: there is no such recognisable animal (as the past subjunctive) in English with the exception, for some speakers, of were for was in two of the six persons of the past of BE.
My opinion is that 'recognizability' (based on what are ultimately mere coincidences of spelling/pronunciation) is no more a valid consideration in this case than it would ever normally be in the realm of grammatical analysis, any more than it would be with regard to, say, 'fast' as an adjective versus 'fast' as an adverb, or 'put' as a present tense versus 'put' as a past tense.
As teachers, we owe it to our students to label the tense-form that appears in the protasis of any second conditional a past subjunctive, and not for any ethereal reasons of academic 'purity', but simply because it serves ultimately to avoid the greater confusion that may ensue from our attempts to 'dumb things down' by pretending that it is just an indicative (simply because it looks like one).
To be precise, without a formalized concept of a subjunctive, we are likely to encounter one or more of the following problems:
1. The difficulty of explaining away the fact that sometimes, for no apparent reason whatsoever, English preterites stop referring to the past, and refer to the
present, or even the
future.
2. The difficulty of explaining away the fact that sometimes, for no apparent reason whatsoever, English preterites actively assert the
unreality of the event or condition that they denote.
3. The difficulty of explaining away the fact that sometimes, no for apparent reason whatsoever, the first and third person singular of the preterite of 'be' switches from 'was' to 'were' (obligatorily so in formal AmE).
N.B. The latter phenomenon simply does not qualify as a 'fixed phrase', since it is not 'fixed': that is, I can insert any verb at all after the 'were' of
If I/he/she/it were... and what follows will be structurally correct, yielding tens of thousands of permutations. It is a
construction,
not a fixed phrase!
You remarked earlier that you did not find it 'helpful' to invoke the term 'subjunctive' when the form in question enjoys near-complete homomorphicity with the indicative. Given, then, the above-listed pedagogical problems likely to arise from a denial of (or, at least, deliberate failure to signal) its existence, is that near-complete homomorphicity not in fact the most compelling reason of all to teach it, since the student has virtually no extra verb-forms to learn, simply one single new
grammar term?
Most intermediate-advanced English-learners that I know are more than capable of, to use the vernacular, 'getting their heads around that'!
