It is likely that the teacher will need to make announcements during the class. When this happens, do not quietly continue your conversation with students. It is natural to want to finish your conversation with the students, but stop talking so that you and all of the students can listen to the teacher. Make sure to stop talking even if not all of the students stop talking to listen.
Example: "Let's pause to hear what your teacher says!"
See this and related tips as a Tip Sheet: http://csteachingtips.org/Tips-for-classroom-volunteers