"You’re supposed to" seems dubious, interpreted either as "be scheduled" or "should". How can I interpret it?
W: That’s very sweet of you, but I can take care of it. Why don’t you do your homework?
M: Oh, I’ve already finished it.
W: That’s great. You just sit there and tell me about your day.
M: Okay. Oh, can we talk later, Mom? I forgot to buy the tickets for the soccer game.
W: Right. You’re supposed to take your brother to the soccer game this Saturday.
M: Yes. I’ll be back soon. It won’t take that long.
Student or Learner