Do Writing Classes Help People Become Better Writers?

I've never taken a writing class, so this blog will be purely speculation. I'm involved in an interesting discussion on LinkedIn about the value of getting an MFA or even an  MA. My question is, how beneficial is taking a non-credit writing course? I've encouraged Julie Cannon, who now has six novels out and, I believe, has another about to be published, to teach a course in building plot. I know that if I attend the course, I'll benefit in that I'll be more disciplined about writing every day and I'll be energized by the group. The question is, will a writing class actually help me become a better writer?

The LinkedIn group seemed to agree as a whole that classes can't make someone better than they have the capacity to be, but classes can help writers become their best more quickly than they would have if they worked alone. When I think of all of the great or even really good writers who attended the Iowa Writers Workshop, to use one example, I have to say that I think the workshops must have made a difference, perhaps helped writers find mentors or just helped them take their writing seriously.

Then, of course, you have the benefit of peer pressure. A professor once told a class I was in that the best writing teacher he ever had was a drunk who never bothered to grade papers. Instead, he brought the papers to class and put them in one of those old machines (can't remember what they are called) that projected the paper onto a screen. Students spent the entire period critiquing the paper--day after day, week after week,  throughout the entire quarter, they judged each other's writing, knowing that their paper could be next.

Dr. ___ claimed that he learned more about both good and bad writing from the drunk professor than from anyone before or since and saw more improvement in a class than he's seen again. Adults aren't really so different from eighteen year olds when it comes to peer pressure. 

Perhaps the real benefit of a writing class or workshop is knowing that peers will be critiquing your work.