This feature is currently rolling out for G Suite for Education or G Suite Enterprise for Education licence users. Google has stated that it takes about 15 days for the feature to roll out completely, meaning that it may not be available for all Google Meet subscribers immediately.
Also, users will have to be logged into a Google account to attend online classes over Meet. By blocking of anonymous users from accessing meetings, Google Meet aims to solve the rising cases of miscreants and other unscrupulous elements bombarding online classrooms and causing havoc. This new feature from Google will help reduce distraction during school hours and ensure that students maximize the time spent in online classrooms. As more schools have turned to the internet to continue coaching during this pandemic, this feature from Google Meet is important to ensure a hitch-free learning experience for the students while ensuring that their online meetings are secure from intrusions by unwanted individuals. Admins can disable this feature by filing a request to G Suite support. Once the request is accepted, anonymous users can now join these meetings organized by the admins. PS: Here is a quick tutorial on how to use Google Meet. References
