This might sound like common sense to some, but kids and focus on their classes have a much better GPA and those who focus on the opposite sex.

AND NOW A MESSAGE FROM 'CAPTAIN OBVIOUS': Nerdy teenagers get better grades.

An economics professor at the University of Southern California analyzed more than 20,000 students to see if there was a correlation between their grades and their social lives, and he found one very clear result:  Kids who aren't popular with the opposite sex have GPAs that are an average of 0.4 points higher. That's pretty significant.  Like, a 3.3 GPA looks okay on a college application, while a 2.9 could be a deal breaker.

The theory is that kids who are popular with the opposite sex are less likely to pay attention in class or study at night because they're so focused on trying to date. And here's some MORE bad news for popular kids.  Another new study from the University of Virginia found the "cool kids" in a school are more likely to wind up having alcohol, drug, and legal problems as adults.

So the advice is, control the hormones for a few years and you'll have a better career later in life. Good luck with that.