You're right that abstinence only education in schools doesn't work. What you seem to have missed is that parents used to be the ones who provided the moral compass for their children and much of society reinforced the parents' guidance. Not only is pre-marital sex no longer taboo, it is encouraged and flaunted.
As horrific as the Sandyhook shootings were, they do not represent a trend and they certainly don't highlight any correctable problems with our gun laws. The incident just provided a liberal playbook dream scenario that falsely characterized it as a crisis, offered a "solution" that was nothing more than a set-piece liberal talking point, cranked up a pliable media, and demonized anyone in opposition.