I second Sungkyunkwan Scandal: it's about 4 students in the Joseon Era that attend this prestigious university called "Sungkyunkwan". The female lead (disguised as a boy) studies hard throughout the drama, as well as the male lead (in fact he's the "nerdiest" male lead I've seen yet).
You should probably be wary of this drama, but in When a Man Loves, the heroine is quite ambitious so very hard-working. The beginning of the drama introduces her as a straight A student, and when she's older she continues to work hard -- in fact that's probably her flaw, but I won't get into the specifics :/ (Really though, if you want to watch that drama you should read all the comments and reviews before...)
The female lead in Autumn's Concerto is very hard-working, she has to be given her conditions.
In One Pound Gospel, which is overall a pretty silly drama (still pretty enjoyable though), the main lead has to work hard since he's a pro boxer. I guess it's kind of similar in Buzzer Beat with basket ball, although I can't remember that drama too precisely.
The boys in Shut Up Flower Boy Band work very hard for their band -- the whole drama is practically about that!
