AITA for switching worksheets on my students who are copy/pasting each other's work?

I teach high school history (grades 9-12), and have been developing digital worksheets for assignments where the students read through sections of the textbook that I don't cover in class. I try to make these as open-ended as possible, so they can focus on what they think is the most interesting/relevant information, but sometimes my students will message me their identical assignments back and forth. The assignment is worth only 40 points, so it's honestly not a big deal but I try my best to make it clear to them that historical events are not a one-size-fits-all kind of deal.<br><br>My solution to this was to give a slightly different version of the worksheet to half of the class, and a "normal" version to the other. I pick and choose some of the questions/topics from the original sheet and swap them out in the second version, so it's impossible(for them) to get away with copying work. There's also a little note I add to the second version, just below the questions, but above the textboxes that says something like "By completing this worksheet, you are agreeing that you have not, nor do you intend to plagiarize another's work".<br><br>This has been working out pretty well, and I've gotten a huge decrease in plagiarized assignments. Some students in both groups have messaged me about it, asking why they don't have the same questions as their classmates. I just tell them that I want to see if they can actually do the work, because there will be plenty of standardized tests where you just memorize answers and questions in your classes. That usually settles it, and the assignments are well-received. I give them credit on the assignments where they don't have answers, and always give them more points for completed work than for skipped work.<br><br>Recently, one of my students who got the second version had their parents email me about a 'lack of transparency' for hiding the note at the bottom of the page. Their parents bought them a plagiarism detector software, and when they realized their child hadn't plagiarized, they obviously got frustrated. I explained my methods above, and they told me that my way of doing things was messed up because I was trying to trick students into plagiarizing, so I could punish them. The email ended with 'This is how students end up hating history'<br><br>So AITA here for trying to get students to do their own work? Or should I just let them copy/paste for the sake of avoiding drama?