SUPPOSED TO
SUPPOSED TO is a tricky phrase with several different meanings. In this context, it describes a rule which is frequently broken.
We are supposed to be at work by nine o’ clock.
When someone says that we are supposed to be at work by nine o’ clock, they are implying that people do come to work after that time.
Note that SUPPOSED TO is preceded by the BE verb:
Wrong: I supposed to finish this report today.
Right: I am supposed to finish this report today.