I was in high school in 1969, knew some calculus, and was very interesting in programming. In a good size city with a major engineering university and a large high school the main barrier was access to computers. Our school had teletypes connected to a remote mainframe. My friends and I found a few computers at the university we could use at night, but most had card readers and line printers, and none had graphics terminals of any kind. I think the particular combination of skills, interest, and access would have been pretty rare at the time.