I think / believe he was originally going to graduate in 2017, but opted to do a prep school postgraduate year which pushed him into the class of 2018. So, on paper he should be set to graduate in 2017 even if he doesn't go to prep. I say that not knowing anything about his grades, fulfillment of core courses, or standardized test scores--obviously, if he can't check all the right boxes, then him reclassifying to 2017 is a moot point.
But if those check out, then essentially he'd be looking to just graduate on time instead of doing the additional prep season.