If you go to the various newspaper articles about the Connecticut shootings, you'll see a lot of raw emotion on display. It is vitally important that sensible people get out there and engage those conversations, pointing out that such tragedies are actually not typical of murders the United States. It is also important to emphasize that the sort of people who commit these random acts of mass murder, are not typical of Americans, or of gun owners. The common characteristic of these sorts of crimes are people with histories of mental illness.
I would not encourage anyone to argue that we just need to arm the teachers. That sounds pretty silly, and realistically, few teachers would do so. More importantly, it fails to address the root problem.