Schedule a single exam and that's your grade for that subject? That's how it should work anyway, credits for work during semester (or worse attendance) are not needed to evaluate if someone learned the material, give them an exam and done.
Which to me seems the best way, you still have to learn throughout the year. Especially to avoid cheating this works nice. And as an aside, most people I know that did a year abroad in the US got 1-2 grades higher, as it was quite easy to just farm extra credits.
At my school, tomorrow is the last day of exams. Most of the students have left campus. There's no time or mechanism to schedule an(other) exam.
Using attendance is a carrot to get students to show up, which leads to better learning outcomes overall - which should be the goal.