And, it's really easy to impersonate someone!
So, I wonder how long it will take for a teacher to get in trouble for belonging to a group they were added to by a "friend."
I don't know how many more times I'll need to say this, but I'll add this additional time to the pile of others: Facebook is a business, and Facebook only cares about your interests up to the point where they can study them and profit from access to them. That is why they allow you to "connect" with things. Any benefit you receive is purely incidental.