You are moving the goalposts. What is your reasoning for selecting $80k as what you consider a “high-paying” job? Is it just because that is what your son was offered and you are very proud of him? Otherwise it seems completely arbitrary. Further, what constitutes high-paying will vary pretty substantially geographically.
Here is an example of how these starting salaries can vary for aerospace engineers:
Los Angeles: $76,534
Indianapolis: $67,954
Do you think that the engineers in Indianapolis just, on average, had lower GPAs than those in Los Angeles? Of course not. Now, let’s look at cost of living adjustment.
Indianapolis Salary: $67,954
Salary to maintain the same quality of life in Los Angeles: $104,653
Sources: Salaries from Salary.com, cost of living adjustment from Bankrate.com
So, which engineer is actually in the “high-paying” job? The one in Los Angeles is probably renting a 1,000 square foot apartment. The one in Indianapolis probably owns a 3,000 square foot house.
Stop picking random criteria for what constitutes a good job.
You can conclude however you wish. However, I hope that the rest of us in this thread have made it clear to any future readers that this is an incorrect analysis of the situation (or at the very least, an overly simplistic one).
You ought to take a course on statistics. You cannot prove a hypothesis with n=1.