Hi Gary Molloy, Vanessa Palmer of Hiawatha Academies offered a suggestion to your question on the Data Champion Hub, another online forum for data analysts in the education space. Does that help you out?
This is the first time I've ever posted here so I may not be very clear... It seems to me you are asking how to compare one class vs all other classes. You can do this using a parameter and a calculated field. In my example, I just created a list of students, their class and a parameter "Student Class" which you select in a parameter control. I created the calculated field that creates two groups - the class you chose and all others. See the additional sheet I added to your workbook -Class v All Others.
Hope this helps.
Cohort Analysis for Help.twbx 76.4 KB