For example, you can add 0.5 avg for the next exam overall grade of students.
1. Create a calculated field to get the current avg for all students.
current avg = AVG([Grade])
2. Create another calculative field as
target avg = [current avg] + 0.05*[current avg].
3. Calculative field to compare whether the reached the milestone/target.
IF [Current avg] >= [target avg] THEN "Reached"
ELSE "Not Reached"
The above field can help you see whether the class has reached the target.
Hope it helps you.