How would it be if I ruined my friends grades in class?
Are you serious? Why do you want to ruin his grades?
Because I'm jealous of his talent in the classroom.
It's wrong to ruin your friend's grade just because you are jelly. You shouldn't do that especially to a friend.
It's going to be funny when he gets a C.
While you think it might be funny it is awful to ruin someone else's future. Don't you think he will be mad or you will get in trouble? I doubt it would be hard for him to prove someone else cheated.