Did you see this thread?

I went to college for everything BUT design. Afterward, I just took the minimal technical courses at night until I had a portfolio. The night design courses, with 30 or more students, were a complete waste of time; the teacher was less talented than I was! Everything I know I learned on my own or on the job. We are all self-taught every time we get another software program and we all keep up on our own.

Mentors and internships are the key way to get into most fields; if an art school gives you access to the right mentors and internships, then that's your justification for going to art school. Strong portfolios lead to more work as you network and become appreciated. No client ever asked me about my formal education; they just want to evaluate my samples.

Even as screwed up as the school I’ve been at is, I still learned a hell of a lot from studying under the lot of talented and successful working designers who teach there, much more than I did from my internships. Michael Beirut wrote about there being two kinds of design programs, crazy fine art programs where students learn about art and how to do wildly creative work, and schools that help students churn out a really slick portfolio that will get them a job. If you go to one of the former, you’ll learn a hell of a lot and that paper really will mean something. The important part is making the effort to find the right school.

The downside, of course, is having to put up with batshit crazy design teachers who have boring clients and live vicariously through their students.

If you get an internship in the field you want to spend some time you'll learn way more than taking general design classes for 4 years. And you might get paid. For me design school was more of a place to mature and experiment in a safe environment. If you don't need to do that, don't.

Like MondoB I have no formal design training - studied fine art in college. Took a few useless night school courses too. Really learned on the job. I don't think a design degree is at all necessary to become a successful designer. It's more about networking, having a really good attitude, taking whatever they throw at you on the job and doing it without complaining, being resourceful, and trying to befriend the senior designers with the hope that they will give you extra responsibility.

Frederic Goudy didn't have any formal training either.