If we remove one of the causes of resentment, we might shrink the desire to kill everyone at school. One less straw on the camels back, so to speak. We may enjoy a politer society as well.
Removing the choice tool of the mass killer would not treat the underlying cause. Murder can still happen with a variety of other tools. If the murderer is savvy enough, they can kill hundreds more without a gun, which they may develop if forced to seethe with hatred over a longer period of time. I believe treating the cause, rather than trying to remove the means is more effective and better for society in the long run.
Many people don't know this, but bullying is abuse. It hurts people and makes them feel angry inside, and they want revenge. If we could only stop bullying, then people wouldn't necessarily have any reason to want to hurt them. Most bullying happens at school, that's why the shootings are at schools more. Bullying happens most at High School, too.
School shootings stem from many different problems some of which are bully related. While putting a stop to bullying would not stop school shootings, it would lessen the chance that they would occur. If you want to stop school shootings entirely you will have to solve other problems as well. Ultimately taking measures to stop bullying is a good start.
Firstly, I am an Assie so I might not have as much knowledge as others from the US but what I have heard is pretty bad. There are morons who go out into school grounds and want to seek revenge because they got bullied in year 5 or hate a teacher (say).
The majority of students who cause school shootings aren't the most popular or sociable kids. Most kids when bullied to a point where they want to cause harm to themselves or others, don't have many friends and their home lives are no better. They have no one to talk to. Having one friend, one person to talk to, can really alleviate stress and depression for a student. Stoping bullying would show kids how being different isn't a bad thing, and that communication is key in any situation.
I believe that more strict and responsible gun control is the real secret to stopping school shootings. In Europe, gun laws are much stricter and we see far less gun related crime and ,specifically, far less school shootings than in America. The fault of the American system is that the government fails to see the negatives of arming more and more people. If less people have weapons, then gun crime goes down because there is less need for criminals to be highly armed. Take European countries with unarmed police forces for example, we have much much lower gun rates than countries with armed police forces because the criminals don't need to fight fire with fire. If you give the police pistols, the criminals get sub machine guns; If you give the police sub machine guns, the criminals get assault rifles. If America simply made gun laws stricter, it would reduce the availability of guns for use in school shootings as well as decreasing armed crime rates also. It is really the best option.
In relation to reducing bullying to help the problem, it will never work fully towards stopping the problem. Most times, bullying goes unstopped due to a lack of effort to stop it. Some students don't report it and those who do are often never fully helped with the problem. While increased anti-bullying policy would remove some bullying, it will never fully remove it. And that comes back to removing weapons for the victims to use to get revenge.
Best solution: De-militarise the american populace to decrease gun related crime.
That is because you can't really stop school bullying. That is because it is part of nature. In nature, the goal of any organism is to survive and procreate with the most suitable mate. The way to get the best mate is to either be the most suitable mate for them or to at least look like the most suitable. Often this mean they degrade the competition by some form of intimidation. In humans and a few other species, this is not just to get a mate but to be seen as the best among those in your own gender.
School kids in general tend to exhibit these traits but it becomes more common in high school when they become teens. Puberty tends to spur this on as the competition become more relevant. A teen feels that the more they pick on others, the better they look by comparison. Clearly bullying will always exist so thinking you can stop shooting by stopping it is foolish.
If you look at school shooters they already had problems. For Columbine, psychiatrists determined Harris had a Messianic-level superiority complex. Klebold had major depression which they thought contributed to Harris being able to talk him into helping him. If Harris had decided not to do a school shooting he probably would've done a rampage somewhere else at a later time. And had Klebold not been talked into participating in a shooting rampage he probably still would've fallen for some "this will give your life meaning" sales pitch at some point.
Maybe there are some cases where had it not been for bullying no shooting would've happened. We don't have a time machine to go back and set up experiments with so we can't know for sure. But even in those cases you could probably also say had it not been for poverty, had it not been for the child abuse or neglect, had it not been for the breakup, had it not been for failing a test, had it not been for an untreated or poorly treated mental condition then it would not have happened. The bullying would've just been one factor out of many, not any more or less responsible than the other factors.
The reason Columbine happened, which left over 10 innocent children dead and many more wounded, was because of bullying. People are all different, so if someone gets bullied, they may snap and lose their mind. You never know what's going on in someone's head, since some may be the quiet type and you don't realise until they do something terrible like this.
Bullying isn't going away anytime soon even if you make it a crime. Children have to assert their dominance after leaving the sights of their domineering strict parents to imitate their parents by stepping on a kid of their age. School shootings can be seen as just another way to assert dominance and a way to purge the weak ones.