Question: I have a pretty high GPA (3.89 Unweighted; 4.35 Weighted), but a low class rank (96/300). How much does this affect my chances at an Ivy League school? Do they care more about GPA or class rank?
College admission officials care the most about your grades in the most challenging courses, especially in your junior and senior years. So both the overall GPA and the class rank will take a back seat to this.
For instance, if you have elected the most demanding classes offered and get all A's in them this year and next, but your rank was torpedoed by some lower grades in your freshman and sophomore years, admission officials will pay the closest heed to your good grades in the tough classes. Or if your rank was actually hurt because, in addition to AP or honors classes, you also took unweighted electives, then admission offcials will realize that even straight A's in subjects like drama or ceramics or shop can lower a GPA more than simply signing up for study hall. (This may sound counterintuitive, but it's true!)
So, overall, it's your grades and not your rank that count the most. But do keep in mind that, at the Ivies, your "competition" will include students who have straight A's in the hardest classes throughout high school. But also at the exalted Ivy level, grades, rank, and GPA alone rarely push a student into the "In" pile. If you don't have other talents or an atypical background, then you will have an uphill battle ahead of you, regardless of your transcript.
But, meanwhile, just keep focusing on your grades and other passions and don't worry as much about your rank.