More aggressive kids?

So this year I took an elective course, and it being an elective, it is not an advanced cl like I've had most of my life. As I've been in this cl I've noticed that the slower kids with lower grades seem to be more aggressive in nature and really aren't friendly. I was wondering how this could be caused and if there has been any link between IQ and aggression. The only inference I could come to was predisposition of some sort.