Let’s understand the difference between the above statements.
Supposed to is used when something is required to be done as a part of rule or law or preplanned action.
Should is used as a general advice to someone.
You are supposed to come on time- This means that as a rule ,it is essential for you to come on time.
You should come on time- It is advisable for you to come on time.
Other Examples of supposed to
He is supposed to come by now. (If the arrival is planned in advance)
You are not supposed to do this. (If something is prohibited)