1. Update Teams
On the computer in the classroom it is necessary to update MS Teams before the first lesson if you want to work with it during the lesson (the update button appears in the top bar, approximately one minute after turning on Teams; see picture 1).
2. Check input and output devices
After the update, don't forget to check your output and input devices in the Teams settings to make sure your microphones and audio are working as you need them to. This check is important to do whenever you are teaching in a different classroom, as some classrooms have different devices than what you have set up in your user account from the previous classroom. Attached below is a screenshot highlighting the section with the settings for these devices (picture 2).
You can find which devices need to be set up in a given classroom on the printed instructions right in the classroom (on the teacher's desk).