I had exactly the same experience in one of my data structures classes. It was fairly late in the morning (maybe around 10:30), but as soon as the prof started speaking I conked out. My only explanation was boredom -- I ended up switching majors, and only experienced that level of drowsiness in one other class during my academic career.

I can't help but think that it means "you're in the wrong place."

I've experienced similar, no matter the class start time. I think I'd agree with your assessment of "you're in the wrong place" not necessarily because of the subject matter, but because of the presentation and environment in which it occurs.

For example, in my high school AP Calc class, I often couldn't stay awake because I picked up on the concepts very quickly whereas my peers did not and I would quickly get very bored when being lectured on the same topics day after day. Contrast that with the amount of books on Mathematics I currently own, that my favorite language is Haskell and that I currently am employed writing software.

It was almost as if my body had developed a heuristic for how useful today's class was going to be and reacted accordingly. The same sort of thing happened through college (Psych, Business, etc) whereas I was known to read psychology textbooks for fun when I was very young.

I need to add that unlike you, I was actually completely left behind on these classes. Younger I felt what it was to understand too fast and I just doodled while people where catching up. But in college it was the opposite.

Sounds more like you were both sleep deprived and not up to speed on the material.

Sleep deprived not at all. As soon as I quit the room I was fresh again. Up to speed is part of the answer, still, the effects were quite astounding. The only experience close to that was blood sample fainting.