I listed on my common application that I was taking an AP Literature class for my second semester senior year, but after I turned it in I dropped the class for the normal English IV class. I never informed my colleges of this change in schedule.
I was accepted to Harvard. Is this a problem? Will I be rescinded for neglecting to tell this change?
Does this count as lying to the admissions office? How should I approach the solution?
Not to worry, that’ not the kind of information that will get you rescinded. You can, however, be pro-active and inform Admissions now about the change in your schedule since submitting your application.
Your probably should have asked about this before being accepted! It won’t make any difference, but I would certainly tell them now. Did you intentionally avoid telling them? Did your guidance office say anything? Again, this is no big deal but the fact that you are thinking about it now makes me wonder if you thought about it before, honestly.
Oh- you have another thread asking about being rescinded for getting B’s. You seem especially anxious about being rescinded 
Maybe you have imposter’s syndrome (look it up) and are worried that you don’t really deserve admission to Harvard. If you are truly anxious, or if there is some deeper thing going on beyond senioritis, please think about getting ahead of it by seeing a counselor.
Change “can” in the above sentence to “should.” It is extremely unlikely that your admission will be affected, but colleges generally don’t like surprises.