Op here. As most teachers will tell you, kids cheat all the time and badly, too. I usually write my own tests and worksheets and only write up answer keys when I need them, which does cut down on cheating. I didn't even realize I had a teacher's edition of the textbook until I came across those answers. On that day I had a family emergency and figured book work practice for an upcoming test would be fine. I did talk to the students involved and their parents. Unfortunately, several of the kids involved are habitual truants and failing my class anyway, so suspension, detention and a zero on the assignment don't mean much to them. A few of the kids involved, though they struggle, do come to class everyday and try, they just made a stupid decision. After a long (and embarrassing for them) talk with me, they (hopefully) have learned a lesson about cheating and blindly following others.