Once again, this academy feels ass at its job.
TF do you mean you regularly let your students straight up die and expelled someone who would go on to become an S-rank adventurer?
I'm not seeing anything to convince me that the realized potential of 100 people who didn't make it through for every one that did couldn't work together to beat that one that did. Not to mention graduates almost certainly come out of it with major personality problems.
I would believe it if it turned out that the whole academy was part of some conspiracy to weaken humanity's overall military might for some kind of demon invasion or something.