School shootings are an interesting thing. They are very rare, but get huge ammounts of attention. For instance, when there is a school bus accident (another rare thing) where students get killed. Rarely is there a call to action in every school in the nation.
The risk of violence in schools, which has been declining steadily over the last 20 years, is overestimated in the public's mind. A recent Gallup poll found that 30% of the people polled felt that it was "very likely" that a school shooting would happen in their school. A student is five times more likely to be killed going to or from school than in it. In fact, school children are the least likely to die actually in school.
Think about that next time it is proposed to have additional security measures such as metal detectors in your or your child's school. This money could go to instruction.