The general thinking that good students will be good workers goes along these lines:
While these are valid arguments, there are other considerations for a student's academic performance, such as:
Personal factors -- Perhaps the student has many personal conflicts with jobs, family (e.g., newborn baby), and environmental (having to study in a loud, distracting place).
Social factors -- Perhaps the student gave up a social life to have academic success. While that is honorable and noble, will such a person make a good employee in a highly social environment?
Personal motives -- Was the driving force behind the academic success an unbearable parent, for example? Will that same force be present in the work environment? Did the student learn for the right reason or just to alleviate another problem?
Poor Student -- Some people, I am convinced, are just poor students. But that does not make them poor or even marginal employees. Some people just do not thrive in a classroom environment but do in a work environment.
I worked on an IT project several years ago with a group of seven or eight academically-successful people. One older lady in the group did not have the college degrees that the rest of us had. She even had limited technical skills and was used on the project as a technical writer. But she had a way about her that brought out the best of everyone on the team, even though she was not the project manager. I remember watching her interact with the group, thinking, that if we were to name an MVP for the project team, it would be this lady; even though she made minimal technical contributions.