I suspect that there may also be regional and subcultural variations. I would never have called any of the adults at my elementary school by their first name-- my teachers were all Miss this and Mrs. that and, later, Mr. whatever. (In nursery school I was very proud of being able to distinguish Miss from Mrs.)

But my parents' friends were Ronnie and David, or Morty and Elise. (At this distance, I'm less sure about my friends' parents-- I think they were mostly still Mr/Mrs, unless they told me otherwise.)