When we put out our pumpkins a week in advance I asked my husband how long before you think they will be gone or smashed. This treatment of pumpkins has been going on since the beginning of time. I tried to teach my kids right from wrong and absolutely would be unhappy if they did such a thing ,however, if they did I would be just as unhappy if someone made a huge deal out of it. Especially when you know that it for the school prank. It’s just a pumpkin.
If I lived in your area, I would have a few extra pumpkins so the kids could take some for their tradition then I would have my extras to put out on Halloween.
Not encouraging the behavior but not a big deal in my opinion. Kids can and do much worse things.