The activity log currently has the ability to filter by video/exercise/article, date and course mastery.

As a teacher the date is useful the other two are not particularly helpful.

What I REALLY need is a way to filter by subject. If a student uses Khan Academy for both Chemistry and Algebra 2 I want to see one subject at a time. If the student has say 150 total learning minutes in a week, I think great! Then if I start scrolling through it and realize they spent 140 minutes in Chemistry and 10 minutes in Algebra 2 that's a completely different story and is not longer good.