Absence as entitlement

I have been teaching a course to second year students of MBA. The rules of the institute require every student to have 80 percent attendance.  Otherwise their grade is dropped by one point.

Some of the students take it that they are entitled to remain absent in 20 percent of the classes. Paradoxically,  they have paid tuition fees for all the classes.  They are not employees. Amusing and irrational behaviour.