In my lower level courses, I tend to have short writing assignments due over the course of the term. Students have 15-18 opportunities to write these, and need to do 10 of them.
It's not really a predictor, because the semester is almost over, but let's say that there's a serious correlation between people who finish all 10 short assignments and people who do well overall in the courses.
I grade these on a 1-10 scale. And I usually give a few extra credit opportunities, too. So, one student in one of my courses has finished all of the short assignments, and done well on them, and done all three extra credit possibilities. And this student has about 124/100 on that part of the course assignments. And I have a student who's turned in two of the short assignments for a total of 15 or so.
Turn up every day, turn in the work, pay attention and take notes, and you'll probably do well in my courses.
Miss a lot of classes, don't turn in work, and you probably won't do so well. I wish I could convince all my students of those correlations.
The extra credit mostly firms up the grades of those who are already earning good grades. The students who don't do the regular work usually aren't doing enough extra credit to make much difference if they do any at all.
I'm ready for BS excuses to end.
Speaking of showing up to do the work: my little finger needs a lot more practice! I have a continual earworm of the piece I'm working on for violin. It's not the most exciting or beautiful piece, either. Alas. (But I am improving on it, slowly.)