In the U.S. the variety of forms of address used is quite broad. I think that at the college level, the honorific Professor is most common, after which the honorific-plus-surname form Professor X (for example, Professor Johnson) is common, followed by the form Doctor X (for example, Doctor Johnson). In graduate school, many students address professors by their first names, particularly in seminars or less formal groups. When not present, professors most often are called by their surnames (for example, Johnson), and less frequently by first name or by honorific-plus-surname forms.

At the high school level, forms like Mr. X, Mrs. X, Ms X, and Miss X are common, where X is a surname. Both in class and out, popular teachers often are referred to by title plus first letter of surname; for example, a Mrs. Thompson might be called Mrs. T.


At the school I attended in England we called our teachers Sir. That may not have been mainstream and I doubt very much whether it’s in use in many schools today.