Good point. Any number of my former students could be suspects.
And you’re a teacher, so you have a big pool of suspects.
I would look at the things the person has done, which business they’ve “ordered” services for you from.
Like ordering USPS mailing supplies for you. Easy to do, but not common everyday well known information unless that person has an internet business???
See if you can connect the dots between the types businesses they pranked you with and the personality or activities of someone you know. People tend to use the things and places they are familiar with.