Google has added safeguards to education accounts for Google Meet, preventing anonymous attendees from joining a meeting using just a link. By default, meeting organizers will need to explicitly invite attendees.
With everything going on in the world these days, you may very well have missed a deft move Google made in the video conferencing space about a month ago.
According to TechCrunch, Google is making Google Meet free and unlimited until September. After that, it will still be free, with meetings limited to 60 minutes.