This is the trouble with cheating: there are no acceptable rules, or laws. It could be a smile, or dancing to a song that you considered to be indefinably 'ours'. It can feel like cheating to go to a restaurant that you used to go to with someone else. Keeping photographs of exes can infuriate, like retrospective cheating.
And this is one of the major questions of our lives: how we keep boundaries, what permission we have to cross boundaries, and how we do so.
Experience has taught me, when I am shaving of a morning, to keep watch over my thoughts, because, if a line of poetry strays into my memory, my skin bristles so that the razor ceases to act.
We expanded primarily for our people - if you don't offer more opportunities, you don't keep good people.
On the rare occasions when I spend a night in Oxford, the keeping of the hours by the clock towers in New College, and Merton, and the great booming of Tom tolling 101 times at 9 pm at Christ Church are inextricably interwoven with memories and regrets and lost joys. The sound almost sends me mad, so intense are the feelings it evokes.
Besides the actual reading in class of many poems, I would suggest you do two things: first, while teaching everything you can and keeping free of it, teach that poetry is a mode of discourse that differs from logical exposition.