Lemme think, for K-8, my kindergarten teacher, 1st grade teacher, 3rd grade teacher, and 4th grade teacher were “Miss/Ms/Mrs First Name.” The only male teacher in my grammar school went by Mr Last Name. Or “Mr T” (as his last name began with T. He left early on, so I never had him as a teacher.) And the couple of nuns left were “Sister First Name.” (Or perhaps it was their adopted name–I can’t remember if they used their given names or took a new name on the sisterhood. At any rate, it was a forename, not a surname.) High school teachers were all honorific (whether Mr/Miss/Mrs/Ms/Coach/Brother) followed by surname to the best of my knowledge. No first names with or without honorific in high school that I remember. No non-honorific first names in grammar school. College, oddly enough, I don’t remember as well how I referred to teachers/professors. It would not surprise me if some just went by their first name, but my recollection is that most, if not all, used their last name.