What is this short story?

This is a long shot, I’ve already scoured Google to no avail.
Many years ago, probably 7 or so, I was in middle school and one English teacher handed out a short story for Halloween. It was about this young boy who goes trick-or-treating to this old lady’s home and asks for a glass of water and while she’s getting it for him he puts razor-blade candy (or apples, possibly) in her candy bowl. He had been given a razor-blade treat a previous Halloween and it had cut up his tongue/mouth/throat so he has trouble speaking, which makes her pity him. That’s all I remember. Can anyone help me with a story name? Thanks :)