You make the school as safe as possible, which most have already done. My kids school all the entry/exit doors are locked with keypads on them. The teachers have to punch in a code to open them, people can only get in through the front door. You make it as safe as possible, and then you hope it is enough. Taking guns away from everyone because of random acts of violence that might occur is not a solution. Arming teachers, having children see their teacher every day all day? In a police state? How freaky and paranoid would that be? That's a horrible idea. Allowing guns everywhere? Letting all citizens walk around packing all paranoid and trigger happy? Horrible idea.
You make it as safe as possible and you and and pray. K, cuz this is life, and yes in life shit happens. Sounds trite, but it's true. Just like with your car. you make sure kids are in their booster seat, having their seat belts on, and you hope it's enough.
That's a good suggestion, it will deter some criminals from schools that don't have this already.
However, I still feel people such as Dylan & Klebold, Seung Cho will find ways around CTPED (Crime Prevention Through Environmental Designs) like the door locks, or amped school security and whatnot.
There are both irrational and rational perpetrators; CTPED deters rational offenders, but not the irrational ones. You can set a house up for maximum burglary security through technologies but at the end of the day if someone
really (eg. often a maniac or passionately driven person) wants to get into a home/school they will do it regardless of all CTPED implementations. They can smash the window, pick the lock, shoot the guard dog, destroy the camera, bypass the fence with a ladder or with Fiskar shears. The illogical ones are driven by some force (I think this is what happened here) and they will do what it takes to reach their goal, because they have no fear or recognition of the repercussions involved in what they are doing.
Criminals will evolve with CTPED and find ways as time progresses. The drawback with CTPED is that it relies solely on temporal variables, they require constant 'upkeep' to follow the pace with changes in society, and this also incurs money and fees as the end result.
My idea of a fix is harder, and it would cost less to implement. Not a gun ban, as people will get a gun if they really want one. We can try to 'reduce' guns as a go-to solution, remove the ideology that guns are cool (to kids) and the status associated with owning one. This can reduce gun ownership all around, and therefore less likely someone will misuse a gun. (8 in 10 chance compared to 1-3 in 10)
I don't think it is an easy task and will take a long time to see changes, which is my argument's downside.