Watch how people treat a substitute. That’s their personality with the supervision turned off.

A substitute has no history with a group and no lasting power over it, which removes both fear and relationship as reasons to behave. What is left is whatever a person genuinely thinks a stranger is owed. That is why one lesson with a sub tells you more about a class than a whole term with the regular teacher.

When the sub arrives, be exactly who you were yesterday. It will feel slightly pointless, and people notice anyway. It also shows you something useful about which classmates are worth trusting.