Interviewer: What do you work as?
John: I work as a teacher.
Whereas both are good English, both sound a little unnatural to me; not quite the phrasing that a native speaker would use.
Interviewer: What's your job?/What do you do?/What line of work are you in?/what is your present occupation?/etc
John: I'm a teacher.
If however,
Interviewer: What do you work as?
John: I work as a teacher.
is part of a practice exercise, then they are fine.