Is there such a thing as a straight A student? Yes and no.
There are students who, by the time they graduate high school, have received nothing but A’s on their report cards. However, I doubt that the straight A student is a kind of student. I don’t think the straight A student is natural, as though some students get A’s the way that birds fly or fish swim. Put another way, if a sophomore with a 4.0 GPA received a low C on a semester exam, I wouldn’t think something was wrong. I wouldn’t say something unnatural had happened.