(Note: The title is a phrase borrowed from the comic strip Zits. I think it is very descriptive of that type student. They are girls because even though both boys and girls can display this type of behavior, girls of this type tend to be especially prevalent)
GPA girls are the type that believe that the only objective in the school years is to get good grades, and get to a good college to pursue a job they haven't decided on yet. They will happily spend 10 hours on a major assignment, without stopping to think exactly what it accomplishes, or the fact that they could make at least US$62.50 in the same amount of time at minimum wage. What makes them "darling" and "little" is that their mentality is so weird it's cute: they spend so much time on assignments and paying attention in class, but still have to study profusely to get a decent score on an examination. They scold students with poor grades about how they are going to be living on the streets, flipping hamburgers, etc. Never mind that they have no idea what they are going to do themselves.
They seem not to realize that it is possible, through the help of community college, to get a bachelor's or graduate college degree no matter what happened in high school. Even if one fails high school, the GED does not care what grades you got. With this in mind, one could put school as a low priority and instead focus on paid work, developing a stash of money instead of a large debt that the "darling little high school student" will incur from $30K a year colleges. Even though the "darling little high school student" will make a bit more income with the Ivy League degree, the other student will have a stash of money instead of a staggering debt, giving him the advantage.
If you don't believe me consider the following list of some famous school dropouts:
Too many to list!