You have to respect Dolores Umbridge. Of all the teachers at Hogwarts', she may be the most facistic, sadistic, self-righteous, self-aggrandizing, pain-in-the-butt on the staff roster, but you really must take your magic hat off to her grasp of pedagogy and how she applies it.
None of the students in the Defence of the Dark Arts ever learned the subject faster than when she was in charge. Her strategy is simple, straightforward, but most importantly, effective. She alienates herself from most of the student body (except for the students looking for empty titles and commissions), rules by decree and terror, clamps down on freedom, withholds knowledge, emphasizes theory over practice, and instead enforces study solely for the sake of passing exams. Hmm... sounds familiar.
Umbridge is such a horror, Harry and co. decide they aren't learning anything useful from her and they start teaching themselves, designing their own curriculum, and by fusing both theory and practice in their study, they are producing their own patronus by year-end -- advanced stuff for their level. People may hate her affected mannerisms, but, boy, the Umbridge Method brings quality results in the shortest given time!
Wonder if our students would take their subjects into their own hands if we stopped being nice to them, and started behaving more like Nazis and less like their friends? One thing I'll say about the Hogwarts' kids is that they trust and respect each other enough to accept teaching from their peers. What I worry about is that our kids have been raised to be so self-deprecating, so teacher-dependent they won't be able to do likewise.