And Harry and Co were the first to do so since about the first war. And of course, probably a combo of dumbles pulling strings to get good teachers such as mad-eye moody, in spite of him mostly being impersonated by a death eater, and other somewhat knowledgably characters, alongside most importantly, probably the existence of the DA, which functioned for two years or so?
It might be more a glut of competence, and students deciding to source their own learning than the institution. I mean, we do have that history class taught by that one ghost, and the divination that may or may not be next to useless...
Edit: Or I might be wrong on the Aurors thing, since going by the potterverse wiki, there were no new members during the whole period between the wars against the death eaters.