Once again, from the pages of Paul Brians’ usage manual Common Errors in English Usage (to which he allows access at no charge at the Washington State University website, here is a worksheet on if I was and if I were. In other words (as you have no doubt already deduced), this document aims to help students make sense of the subjunctive mood.
This is a full-page worksheet with Professor Brians’ five-sentence reading, then my own lengthy instructions on the sentence analysis work that I conceived of as the principle work of this exercise. In any case, this is a Microsoft Word document, so you may manipulate it for your needs.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.