It makes no sense, but it is the law in MA.
---------------
My town appointed a new superintendent a couple of years ago. He seems like a decent guy and due to his personal background, he grew up in Maine and taught in Alaska, I figured that he's seen a gun or two over his career (in non-threatening circumstances) so I took the opportunity to have a personal chat with him earlier this year. I have no children, so this is easy and poses no risk to myself or Family!
I asked him to put what I was about to tell him in the back of his mind for when this scenario occurs. I explained how easy it was for a kid (or even a teacher) to have picked up a shell casing in a pocket, pants cuff or cleat of a shoe/boot and end up dropping it a few days later in a school without ever knowing that they did it. I stated that I thought that the over-reaction by most MA districts in locking down every school in town, cordoning off a square mile around the school, etc. was WAY OVERBOARD! He responded that they do have to do a diligent check and I countered with "I agree, but suggest that you just don't go overboard like so many school systems have"! We'll have to see when it happens . . . how they respond. There are numerous juniors programs at most gun clubs in the area, it is merely a matter of time.