I think that a great deal of focus has been on more aggressive measures, rather than ones that involve teaching children (and teachers and staff) how to react during a school shooting. I do not claim to have all the answers so please bear with me. When it comes to preventing something, there is only so much you can control, and I think the same concept applies to the school shootings. Unless there are extremely stringent measures put in place (like body cavity search for every student) I think there will always be a possibility that a school shooting will occur.
It might be easy enough to think that arming more people will help deter school shootings, but this has not been tried or proven, so it is hard to stand by that conclusion. I believe that the best way to help end school shootings, or at least deter them, is to teach more people how properly react when the situation arises. This article I was reading (
http://united-locksmith.net/blog/what-to-do-during-a-school-shooting) breaks it down in amazing fashion and I thought it was well worth the read.
It delves into weapons handling, security information, how to hide effectively and even how to aid authorities. I think that using the knowledge in that article and in a few others like it, we can find an answer that is close enough to end school shootings, without inciting more violence.