I'm going to tell some random high school student fake exam information
Why would you tell someone fake information?
I don't think he's worthy of knowing this information. I think some people should not be given what they desire.
I sometimes do social pranks as well, it's fun and it can be really funny when people find out that they were just being pranked. However, exams are very important for people to pass, and it can be a matter of passing that subject or not, and that is absolutely not ideal for you to give people fake information for. How about you play a harmless prank instead, like leaving a fake $100 bill on the floor?
I think it's funny that I'm going to fuck this guy over.
You shouldn't do things that can do real harm to other people. While you might think this is just funny, you might actually cause serious damage to this student's future success.