Academia slang. A top student (high school higher) whos grades are so high that they make their fellow students look bad. Curve comes from the mathmatical term - normal distribution curve. Theory is that when educators rate, they adjust grading scale so that most people are average. The curve dick throws off the curve so the rest of students look worse than they normally would.
Meaning of dick here is "to screw someone over."
Susan's such a curve dick. She got a 97% on the test when the next highest grade was 71%.