That there is a clear distinction in meaning is why the different forms survive in virtually every language on the planet except contemporary English as taught in the American public schools. It survives in street Spanish and street English, just not in the NEA.
Andy, I wasn't going to do this, but now you've made me. LOL.
THE FOLLOWING IS WHY I think we should forget the was and were constructions, and concentrate on such obvious misuses of the English language as, "He gave the book to I." :
>>>The form of verb in the main clause will depend on your intended meaning: If Hamlet was really written by Marlowe, as many have argued, then we have underestimated Marlowe’s genius. If Kevin was out all day, then it makes sense that he couldn’t answer the phone. 7
Remember, just because the modal verb would appears in the main clause, this doesn’t mean that the verb in the if clause must be in the subjunctive if the content of that clause is not presupposed to be false: If I was (not were) to accept their offer—which I’m still considering—I would have to start the new job on May 2. He would always call her from the office if he was (not were) going to be late for dinner. 8
Another traditional rule states that you are not supposed to use the subjunctive following verbs such as ask or wonder in if clauses that express indirect questions, even if the content of the question is presumed to be contrary to fact: We wondered if dinner was (not were) included in the room price. Some of the people we met even asked us if California was (not were) an island. 9
if clauses—the reality. In practice, of course, many people ignore the rules. In fact, over the last 200 years even well-respected writers have tended to use the indicative was where the traditional rule would require the subjunctive were. A usage such as If I was the only boy in the world may break the rules, but it sounds perfectly natural. 10
subjunctive after wish. Yet another traditional rule requires you to use were rather than was in a contrary-to-fact statement that follows the verb wish: I wish I were (not was) lighter on my feet. Many writers continue to insist on this rule, but the indicative was in such clauses can be found in the works of many well-known writers. >>>
http://www.bartleby.com/64/C001/061.html
Do we honestly expect the average student to learn all the above, and if he did, wouldn't he sometimes sound wrong to those who didn't memorize it all?
I once saw a quiz which asked which of the following is correct:
This book is different than that other book.
This book is different from that other book.
The answer was: This book is different FROM that other book.
To my ears, THAN sounded right. So I decided to use FROM only when I was speaking to a professor who knew and used perfect English. That is, until one day when I heard him say, "You handed me the wrong copy. This one is different than the one I wanted."
I give up! Purity in construction is not always desirable.
But, yes, continue to teach it in the advanced classes.