One of the painful ironies of Friday's massacre at Sandy Hook Elementary School in Newtown, Conn., is that a new security system was installed there not long ago.\tPrincipal Dawn Lafferty Hochsprung, who was killed along with 25 others -- 20 of them six- and seven-year-old children -- had overseen the installation of a new security system requiring that every visitor ring the front entrance doorbell after the doors locked at 9:30 a.m.\u00a0 Once buzzed into the front office, parents and other visitors were asked to produce photo identification.\tIt wasn't enough to stop Adam Lanza from getting in. The 20-year-old simply shot his way into the building.\tSince Friday's horror, I've seen plenty of suggestions bandied about on how to make schools safer, including:\t--Giving every principal a gun\t--Installing bullet-proof glass\t-- Installing metal detectors and stationing armed cops in the buildings\tIn my view, all of these actions taken together would turn schools into prisons. That's not the America I want my children growing up in. Besides, none of these things would have been enough to stop a guy with a Bushmaster AR-15 rifle with magazines containing 30 bullets each from killing a lot of people in the blink of an eye.\tI'm not saying we throw up our hands and give up on making school buildings more ironclad. I'm simply noting that 100-percent protection doesn't exist. The best we can do is slow the attacker down and minimize the number of people he can kill.\tOf course, I'm not telling you anything you don't already know. This is just some of the pondering I'm doing this Monday morning as I -- like everyone else -- continue to absorb the magnitude of this tragedy.\tI'll end by thanking you all for your continued efforts to improve physical and Internet security. You may not be able to save everyone, but you are making a difference.