One of my college professors always starts a new session by telling the story of how he bacame a professor. He started off by learning how to be an electrician, because that's all everyone around him was doing. This is in a 3-tier schooling system. After doing that for a while, an instructor encouraged him to go for a somewhat higher learning to become a technician. He did, and there again, he decided on a whim to try out for the university. He got in, and was encouraged to get a PHD. He got it, and some years later, was made a professor.
It would have been real easy for him to have stayed an electrician. Maybe he could have met a girl and needed to pay bills. Maybe he would have felt he was too old. He had the intellectual ability, but the tiered system could have forced him into a path where he would never have been able to contribute what he has to everyone who passed through him.