We're going to get right down to it. Sure, you could try to skirt the issue—certainly, Hardy's narrator seems to—but eventually you'll be confronted with this bare fact: Tess of the D'Urbervilles is almost completely defined by the rape scene. In fact, you may find that your students already know (or think they know) about the novel before reading it. After all, word travels fast when sex or scandal are involved.
Of course, once students actually read the novel, they might feel more than a little thwarted. It's not just the writing style, which, let's be honest, demands a deep grasp of the English language. It's those seemingly unending descriptions of the English landscape (who knew so much could be written about cows in the pasture or a steeple in the distance?) and the lack of a very central piece of description: the rape of Tess.