Yes, we all know of exceptional people who are really smart, though they lacked the ambition/money/whatever to finish high school/college. But they are just that -- exceptions to the general rule of thumb that someone's education level is usually a good indicator of their intelligence.

Rather than citing personal examples back and forth, consider this... if you had a doctor, lawyer, computer programmer, psychologist, and professor on the left, and a trash collector, fast food grillboy, Wal-Mart cart pusher, (non-Good Will Hunting) janitor, and a burnt potato chip picker (the guy who sits there and watches the chips go by on a conveyor belt removing the burnt ones... this really is a job, I promise I'm not making it up) on the right, which on average, would be the smarter group?