Set up Circle, assigned your kids' devices to the right profile, and now they can't access Google Classroom or Google Docs? You'll need to make sure Chat and Forums is set to "Allowed" for their profile.
We've classified Google Hangouts and Google Meet as Chat and Forum websites. Because of how Google services work these two websites share server resources with Google Classroom and Google Docs. If you want your kiddos to have access to the above, you'll need to make sure their profiles are set to at least the Teen Filter level and Chat and Forums is set to "Allowed".
Your kids aren't teens and you're worried this filter level is too open? You can always customize the Teen profile filter level to be more restrictive by setting categories or platforms to "Not Allowed". Just make sure Chat and Forums is set to allowed if you want your kids to be able to use Google Docs, Drive, or Classroom!
In an upcoming update we will be changing how Circle handles Google platforms to better account for the above.