Chris Brooks highlighted a Stephen Colbert interview with GameSpy. Colbert started playing Dungeons & Dragons in 1976 when he was in seventh grade. Chris says he started playing D&D around that time as well.
I started playing in 1981, when I was in the seventh grade as well. The eighth grade teacher at my school was into war games and D&D, and a group of us used to meet each weekend at the school for gaming. I remember Ed taking all of us out to the Dungeon Hobby Shop in Lake Geneva. We were pretty impressed that TSR, the makers of D&D were in the same building upstairs. Living in Kenosha, Lake Geneva wasn’t very far. We used to go to Gen Con every year as well. The convention was held at UW-Parkside back then, so I could hop on my bike (before I had a car) and ride over. It really ticked me off when they moved it to Milwaukee.
The core group met pretty regularly up through high school. After that, it was pretty much the end of RPGs for me. Never seemed to have the time.