I managed software developers for many years at a fairly well known software company, where the first gateway for a hire was an advanced Math or CS degree with

I managed software developers for many years at a fairly well known software company, where the first gateway for a hire was an advanced Math or CS degree with an undergraduate gpa of 3.5 or higher from a tough school (undergrade gpa because we felt that was more indicative of raw talent or work ethic than graduate gpa). This was followed by rigorous testing in logic and programming. Even after all that I found there were still between 10-20% of hires who could not code. Many with Masters or PhDs in Computer Science. My theory is that coding is kind of like carrying a tune in music - either you have it or you don't. It's not an intelligence issue or a matter of education. These were bright folks. There is a mysterious innate ability that you must have to begin with, and some just don't.