A new and interesting paper from NBER has some pointers for high school kids and parents of high school kids. Don't be sad, or worst, don't be depressed, otherwise your school grades will go down.
I mean, such relationship between these two is not surprising, but again, with the power of economic thinking, Jeffrey DeSimone has managed to quantify such relationship. Examining the past year relationship between GPA and experiencing a combination of two primary depression symptoms, feeling sad and losing interest in usual activities for at least two consecutive weeks, among high school students during 2001–2009, DeSimone finds that sadness lowers the probability of earning A grades and raising the probability of receiving at most C grades by over 15%. The worst part is the effects are significantly larger than those of having considered or planned suicide and equivalent to having attempted suicide (which seemingly signify more severe depression).
So the point really is other factors can affect the performance of a student that is not related to his or her cognitive or non-cognitive skills. The environment has a crucial role to play, and when I mean environment, it includes what's going on with the family, the student's relationship with his or her peers, and things like that that are outside the student itself. But then again, the student's cognitive and non-cognitive skills may also play a part--how he or she reacts or responds to these outside forces may be important in determining how much of these factors are negatively affecting him or her.