... the hard way.
This semester I started making students tell me they'd be taking the optional final exam.
This afternoon two students showed up for the exam -- but, they hadn't told me they wanted to take it.
I refused to give them the exam. They seemed stunned.
Of course, I announced it in class many, many, many times. It was clear from their grade report last week what they'd need to do in order to take the final etc.
Of course, these two had terrible attendance -- and when they managed to make it to class, they weren't prepared anyway -- so it isn't much of a surprise.
Although, I do wonder if one of them had some kind of learning disability -- or if he was just dense? I'd say things that seemed to be clear to other students and he'd look at me like I was speaking French...