It doesn't matter what we ban, people are always going to find a way to kill other people. As a matter of fact, I think that school staff should not only be allowed to have guns with them but they should be encouraged. When a shooter (or in this case, a stabber) sees that an area is a gun free zone, like just about every school in America is, that doesn't deter him from going in there and loving stuff up. Its not like he sees the sign and thinks "Oh well, that's a gun free zone! Guess I'll have to find someplace else to shoot up, because if I took my gun in there I'd be breaking the law!"
It boggles my mind to see that some people actually believe that putting up "gun free zone" signs are going to somehow prevent shootings, all that does is disarm the law abiding citizens so that it is easier for a gunman to shoot stuff without meeting any resistance.