Most kids who behave violently in school have a long history of emotional and behavioral problems. In many cases, signs and symptoms of trouble have existed for years. We know a lot about the early warning signs and situational risk factors which can lead to violent behavior. Reduce class sizes. In a large class, it's harder for the teacher to really know and monitor kids as closely.
Smaller classes allow more contact between the teacher and each child.
As a result, kids with significant problems are more likely to be identified early. Reduce access to guns. We have to get much more serious about limiting the overall access kids have to guns. This includes age limits on the purchase of guns and ammunition, mandatory trigger locks, increased penalties for illegal sales. Promote tolerance and teach conflict resolution.