You can join a class video meeting after the teacher starts the meeting.
To use Meet, you have to sign in to Classroom with a school account. Your account looks like studentlogin@stisidore.org
- Open the Google Classroom app .
- Tap the class.
- Choose an option:
- At the top of the Stream or Classwork page, tap Meet .
- On an announcement or post, tap the video meeting link.
- (Optional) To allow Meet to use your camera and microphone, tap Allow.
- Before you join, at the bottom, make sure you’re signed in with your school account. If you need to switch accounts, tap Switchselect the Classroom account.
- To join the class video meeting, tap Join meeting.
Taken from: https://support.google.com/edu/classroom/answer/9777280