Your mother was correct.
In a related field, electronics, I have found that the best technicians were not the ones who graduated at the top of their class, but the second tier, ‘B’ students.
The top students usually have a superiority complex and cannot do the actual work, preferring to ‘study’ the problems to death theorizing.
The ‘B’ students solve problems, quickly and pragmatically..............
I can personally state some of those high grade “earners” cheated their way through college. It cost me a close friend, when I admitted it.
They don’t know anything useful, bit it got them their first decent paying job, where they had already learned to “fake it.”