It is rude to interrupt someone's conversation.
Sean needs help with his assignment, but his teacher is talking with someone else.
Sean wants to ask his teacher for help.
Sean waits for his teacher's conversation to end before asking for help.
Sean barges into the conversation and asks her teacher for help.
Sean's teacher thinks that he is polite and is more willing to help him.
Sean's teacher thinks that Sean is rude and obnoxious and asks him to wait.