The issue here is that people are taught to associate drop outs with high school drug dealers, and lazy goofs with no ambition or drive - people who will never succeed on any level, and that's simply not accurate.
I graduated, but my attendance record in high school?
It was uncommon for me to go to more than one class a day. All but a handful of my teachers hated me, and a few openly professed that I would never succeed in life, but despite that I was one of only a few people in my graduating class to get into UBC and actually won a few scholarships.
Performance in high school is less a reflection of intelligence or drive, than it is a reflection of how well you can adapt to that system. I did not fit the system, I adapted to make it work for me, but I was still a square block in a round hole. Once lots of drop outs move out into the real world, they find a system that works for them and excel. Simple as that.