Displaying Summary Field data in sub-summary
I have a data set of test scores, Test1 and Test2. Test 1 is given at the beginning of the semester, and Test2 and the end. I need to calculate an average for each for a group of students - by grade or classroom, and calculate the change in the average scores. I initially used a summary field, Test1_Summary and Test2_Summary to calculate the average of each, and then another field to calculate the difference between the two summary fields. I found that the averages were wrong because the Summary field was including the students who had no score entered, which brought the average down. I then changed the summary fields to total the test scores, and used another calculation field, Test1_Count and Test2_Count to count the number of students who took the test, then used Test1_Summary/Test1_Count to calculate the average.
This worked fine until I laid it out using a sub-summary sorted by grade. If I search for a single grade, it displays fine, as shown on the screenshot below. If I include all grades or multiple grades, and sort by grade, the average summary field is correct for each grade (though technically wrong because of empty fields), but Test1_Summary/Test1_Count and Test2_Summary/Test2_Count shows the same value on each line of the subsummary.
Aren't summary fields evaluated within a subset, as defined in the sort restriction of a sub-summary?