Some schools make no guarantee of meeting full need. That you happen to get it freshman year doesn’t mean you will in future years, if your need changes or if part of the package is comprised of merit awards you lose, if prices go up, if upperclass housing costs more, if your EFC goes down due to unforeseen, uncontrollable events like job loss , Illness of a parent, a sibling going to college ,etc etc. i can list quite a few things
But it’s a whole other thing from extra need cropping up to a college cutting financial aid drastically when the financial situation is about the same. That, is inexcusable , IMO. Who can sleep at night if your kid on financial aid is at risk of having the financial rug pulled out from under him for no reason that makes any sense? This, even at schools that do not guarantee to meet full need. That freshman award should be guaranteed , all things equal, with clearly stated caveats.
As for those schools that guarantee to meet full need, it’s even more of a breach of trust when aid is decreased even as costs go up. There are reasons that can be legitimate for this scenario, but when that happens, it should be made very clear what the change of circumstances are to evoke a lowering of financial aid.