Bullying is just a part of human nature, and will always be pervasive in the schools. The R rating is rediculous, but showing the movie in assemblies isn't going to make a difference. The real problem is the schools and parents that pretend nothing is wrong, our don't take it seriously enough.
I was bullied on a daily basis when I was in 2nd grade. I was the smallest kid, and the biggest kid with his three lackeys thought I was a good target. I faught back every time, and actually did more damage to them simply because I was more willing to actually do damage. In addition to physical conflict they would bully me socially by manipulating the few friends I had. Everyone knew what was going on, but they never did squat about it. It just turns into he said they said, and ground duty sends everyone to the wall. Looking back I'm appalled that it never went beyond the ground duty. It only stopped because the instigator broke his leg in an unrelated incident falling down the stairs. Luckily his family moved after that.
It is a regular part of life that everyone has to deal with to some extent. All the more reason for adults to take a more serious no tolerance approach, and spend more time trying to actively find problems in their infancy.