Tracking activity for a student - breaking it out between classes

My high school students are using Khan for several subjects (with other teachers) so when I look at the tracking of activity it shows total Khan usage, not just usage for my class. The folks at Khan say the system is unable to track activity by class.  Short of clicking on each section of a student's bar graph, does anyone have a suggestion for easily tracking how much time they are spending on Khan for MY class?

Thanks!