How can I call a person who teaches me English, because I always called him teacher, and yesterday my sister said me that it is incorrect, that I have to called him Mr. + last name. Is that true? Can you explain me, please? I am a English student from Argentina and normally we called them "teacher".
In an English school the students would normally address their teachers as your sister suggests:
or if they have a doctorate
If you are being taught on a one-to-one basis then initially you could use those forms of address as a mark of respect. It is possible that the teacher may suggest to use their first name - my wife is a tutor and she tells her pupils to use her first name.
In the UK we rarely use the persons role as a form of address, so we would not say
However, some formal schools do use the titles of certain positions
Thank you Matron
This is not common in today's schools.
In some schools teachers are called "Mr ..." or "Mrs ....", using only their title and surname. (Other titles such as Dr, Miss, Ms are common. The teacher would tell their class what they expect to be called.)
In other schools, teachers are called "Sir", "Ma'am" (pronounced "mahm") or "Miss". Whether names are used is part of the culture and ethos of the school Similarly whether female teacher are called Miss or Ma'am varies from school to school. Larger schools, are more likely to use "Sir". Since the pupils won't know the names of all the teachers. Use of "Sir" is therefore more common in city schools than in smaller rural ones.
A few schools, such as those following Steiner system of education, use first names.