It varies greatly from student to student, I have found. Where many times the Valedictorian of our graduating class has a 4.0, they are often some of the most outgoing, involved students we have. There are others that have to work very hard for their grades.
A Vietnamese brother and sister who were recent immigrants and in the 8th and 9th grade, had to work incredibly hard each day to learn the language, master the subjects and get good grades. They each ended up going to MIT on scholarship, but they did have social issues in that there was never much time to just hang out with friends, go to dances or date.
For students who only work on academics, and stick to such a rigid study schedule, yes, it could be a possibility, but I don't see many of those students, especially now with Facebook and MySpace.
Some of the social handicaps I've seen include nervousness about starting conversations, or being exceptionally quiet in class, even when called on. Sometimes they have a sense of humor or behavior that is a few grades below where they are at in school.