Can anyone think of the term that I've forgotten? We generally applied it to those students who did not have any outstanding intellectual ability, but worked so hard in preparing for courses that they appeared to have more to work with mentally than they actually possessed in terms of original thinking.

May I present one more offering: the person who works so hard that s/he gets much further than one would have thought based solely on apparent inherent ability:

overachiever

And that should be a compliment !