I sense a great deal of cynicism towards educators in general, as well as some pretty big assumptions about the film and its characters. (Full disclosure: I have been a high school English teacher for over 20 years, an DPS was one of my favourite films back when I was in high school.)

First, the question of Mr. Keating's teaching: We see maybe 3-4 scenes in his actual classroom--over what appears to be several months of the school year--and he makes several references to assignments, tests, and papers. It is not like he is burning down the entire educational system of which he is a part. Granted, he has several unorthodox methods and approaches, but there is no indication he has abandoned the content or skills the students are expected to know. As someone already noted, Keating never once tells them that what their parents do--or what the students plan to do--as professions are somehow wrong or devoid of meaning. He is trying to get them to see art (in this case, literature) as a companion to the necessities of life (job, family, bills, taxes, etc.), not a replacement for them.

Second, the kids were already rebelling (albeit in a pretty tame fashion, like smoking) against the norms of their conservative parents' generation. Perhaps they were emboldened in these pursuits by a misunderstanding of what Keating was trying to get them to see/understand about life, but recall the one "phone call" prank from God that got one of them in some trouble with the headmaster. He expects praise from Keating, but while Keating does (eventually) make a light joke about the incident overall, he first calls out the student for being reckless with the opportunity he has been given to attend the school. As Keating tells him, "Sucking the marrow out of life doesn't mean choking on the bone."

Again, he is trying to teach them that art and life (or passions and responsibilities) can be a both/and relationship, rather than and either/or one.

Lastly, look at the sequence of events around Neil and the play: He auditions without telling anyone, and gets the part. He tells Mr. Keating that his father will be upset and he doesn't know how to broach the subject with him. Mr. Keating (who never once tells Neil to lie or hide the information or go against his father's wishes) encourages him to speak about what the play means to him with as much passion as he as done when speaking to him (Keating). Neil follows up a few days later by lying to Keating, telling him his father was initially upset, but agreed to let him stick with the play. Keating (you could argue wrongly, I suppose) takes what Neil says at face value and assumes he is telling him the truth.

Yes, there are a lot of topics and conversations and "takes" on the film, to be sure. But I don't know that one can reasonably hold Keating responsible for >!Neil's suicide!<.