Overexposure to violence in the media can cause desensitization in some young people. Of course, as always there are many other combining factors to consider such as one's home environment, personality, etc. I do not believe there is any evidence to hold the violence in the media solely responsible for students acting in violence; however, there may be a correlation especially in cases where it was discovered that certain violent students didn't have a balanced and supportive home life, and that they were fascinated with particular video games or movies that glorified violence.
Sometimes violence can have a ripple effect. School shootings, for example, can lead to other violent episodes in different places. Suicides have been known to be "contagious" especially among teens. In general though, I would argue that the worst effect of violence in the media would be in creating fear for students. After an incident or threat of an incident, many students do not attend school because either they or their parents are afraid.
As with so many things in the social sciences, this question cannot be easily answered. It is never easy to determine what actually causes people to act in the ways that they do. Please follow the link below to see a discussion of various things that might help to cause vioence in school (at least in the USA).
If violence in the media does affect the ways that students interact, it is likely to make them more likely to be violent to one another. Scholars argue that violence in the media makes young people tend to be more violent themselves. They argue that when young people see many acts of violence in the media, they get used to violence and think it is normal. Because of this, the argument goes, they are more likely to use violence as an answer to their own problems.
how do people become affected due to media portraying violence. ?