My wife is a special ed teacher and has been fighting with this for 3 weeks. Try teaching a bunch of kids who don't get it and don't care. There are a few that haven't been heard from since school stopped. One family went to Columbia and can't come back!! Yesterday she was doing a Google Meet class with 2 kids and she kept getting a popup with someone wanting to join. She has to deny it every few seconds, but can't block it or lock the room from anyone trying to enter. One of the kids (who didn't want to be there) must have shared the link and his friend was ruining the whole thing.