After mulling over the potential cause and effect relationships reflected by that correlation, he came to an interesting conclusion: students who did not work their way through college came from more money, had better connections, and, because of those better connections, started in better jobs after college.
Graduates who started ahead in the race of life, all other things being equal, stayed ahead. Not to mention that students who came from wealth had a reasonable chance of inheriting the family firm, becoming a CEO at an age when others were only dreaming of doing so.
Now here we see a USA Today story reporting the same findings for high school students. Those who work more hours in high school are less likely to finish college. Once again there is speculation about the meaning of the findings.
I suspect the meaning is the same. Those who work are less financially favored, and come from homes where there is less emphasis on education and consequently more emphasis on work and/or idleness.