One of my classes has a final exam. I was planning on actually designing the thing next week, since there's a solid week between the last lecture and the date of the final and I'll have nothing else to do in that time.
Until then, I was planning on working hard to get the last of the grading done, so students will know their grade going into the final. I always liked that as a student, being able to compute exactly how well I need to do on the final to get what grade. I'd like to do that for my students. But I don't really have time to do that AND come up with all of the questions for the final exam.
But then I realized I should really give out study sheets for the final exam (I'm ashamed that I had to be reminded of this by a student). But in order for those sheets to be accurate, I have to know the content of the final...
So, I either have to keep students in the dark about their grades, or keep them in the dark about the final exam, or take a guess of what content I'm going to test on the exam and then try to stick to that. I'll probably do the latter.
Now I know why in some classes, the study sheet would bear no resemblance to the actual content of the final... it's because the final wasn't written until after class was over!