People don't know the cause of school shootings, so they're trying to chip away at the methods used to achieve them. Banning guns, video games, heavy metal, etc. all fit into this in that people perceive these as being contributing factors to why people shoot up schools.
But what makes them want to shoot up schools? I'd say there are two issues here:
1. Mental health, especially undiagnosed mental health issues. In this society, all you can do if someone has issues is either pay for them to get treatment, or start a process that's going to get them confined in mental institutions.
2. Media coverage, because if you shoot up a school and get a high enough kill count, you're going to be on the front page of CNN etc. for weeks.
In this society we have an ugly tendency to assume that methods and not inner motivations, including ability and mental health, are important. We think that memorizing facts is more important than having mental ability; we look at whether people are obedient to social norms rather than whether what they're doing is right.
These types of situations suggest our society has some pathological need to avoid looking at our motivations. Perhaps we're afraid we'll find nothing but making money, watching TV, and eating Taco Bell.
I hope not.