How do I "clean up" select courses in Gradebook?

This is my 1st year using (I’m using the CS Discoveries course for my HS intro to CS class). However, my students appear to have progress in other, older courses.
The issue:
When I go to see student progress, the “Select Course” section automatically loads the oldest course that a student has taken so I have to find/select my course and wait for it to load. This may not seem like a lot, but I have 4 different sections so I spend a considerable amount of time waiting on the screen to load when visiting all 4 sections.

Any ideas??