But it isn't. The question was "X is trying to get into Princeton - an A- isn't going to get her in. What extra credit can she do to make this an A?" Presumably

But it isn't. The question was "X is trying to get into Princeton - an A- isn't going to get her in. What extra credit can she do to make this an A?" Presumably, the extra credit means the student will learn more. Hence, it is not zero-sum. And it actually seem fair to me; the student that works the hardest and scores the highest grades deserves to win the spot.