Wait now, I remember a song when I was in grade school sung to the Battle Hymn of the Republic.

My eyes have seen the glory of the burning of the school
We tortured all the teachers and we broke all the rules
We hung the secretary and we shot the principle
Our troops go marching on

People have always sung songs about how much they hate school. It comes from frustration over having discipline imposed on your life. Both the disciple of having to follow set rules that take away your individuality and the disciple of being told when to be where, what to do, turn in homework. Do they contribute to violence, does it get worse when they are put on the radio instead of snickered at during recess? Its hard to tell. But blaming music and video games or television instead of holding people responcible for their actions is irresponsible, just like having video games or television or even teachers raise your kids for you. Whether or not we have freewill or not is a question for the philosophers, but freewill or no, people need to take responcibility for there actions or responcibility needs to be placed on them if they won't accept it themselves.
Adulthood keeps getting pushed further and further back. Hold people responcible as adults at fifteen and they'll act like adults at fifteen.