Jesse Aguirre’s workday at Slack starts with a standard engineering meeting—programmers call them “standups”—where he and his co-workers plan the day’s agenda. Around the circle stand graduates from Silicon Valley’s top companies and the nation’s top universities. Aguirre, who is 26, did not finish high school and has so far spent most of his adulthood in prison; Slack is his first full-time employer. But in the few years he has been writing code, he has cultivated what is perhaps the most useful skill in any software engineer’s arsenal: the ability to figure things out on his own.