Always check your emails regularly for any emails from your teachers with the subject beginning with "Invitation".
Once you've clicked Yes to your online lesson or assembly your lesson will be visible on your Google Calender App
Ensure to click 'Allow' when you receive the prompt on the right.
Click 'Switch account' if you see your personal email on the top right corner of the Google Meet window.
You will not be allowed to join with your personal gmail account.