Yea, that will stop anyone bent on murder.
I didn't say it would stop anyone bent on murder. I said it's against the law.
I frequently will not think about taking my gun off when I'm going somewhere such as the post office where it is illegal for me to have my gun. But I've never been charged for having a gun where I wasn't supposed to because I've never taken it out and showed it around.
Whether or not these kinds of zero tolerance laws are good or bad isn't the point. The point is, if you have a rifle on school property you are violating the law. You don't then announce the presence of the gun by taking the rifle out of your car to exchange it with someone else in front of witnesses.
This was just poor judgment on the part of the kids.