Expectations: Be Supposed To

(a)    The game is supposed to begin at 10:00. (b)   The committee is supposed to put away their toys before they go to bed.	Be supposed to expresses the idea that someone (I, we they, the teacher, lots of people, my father, etc.) expects something to happen. Be supposed to often expresses expectations about scheduled events, as in (a), or correct procedures, as in (b).
(c)    I am supposed to go to the meeting. My boss told me that he wants me to attend. (d)   The children are supposed to put away their toys before they go to bed.	Be supposed to also expresses expectations about behavior. In (c) and (d): be supposed to gives the idea that someone else expects (requests or requires) certain behavior.
(e)   Jack was supposed to call me last night. I wonder why he didn’t.	Be supposed to in the past (was/were supposed to) expresses unfulfilled expectations. In (e): The speaker expected Jack to call, but he didn’t.