Teacher, headmaster, form mistress, principal ______ ?

The terms "teacher," "headmaster," "form mistress," and "principal" all refer to roles associated with educational institutions and the overarching structure of school authority. These individuals are responsible for managing and guiding the educational experiences of their students. In this context, it is important to identify a word that fits as a counterpart or complements these terms within the educational setting.

Among the provided options:

- A) "child" refers generally to a young human and is not specific to the educational context.
- B) "pupil" specifically denotes a student within an academic setting, making it a direct counterpart to the roles of educational professionals listed.
- C) "woman" is a gender descriptor and doesn't relate specifically to education.
- D) "teenager" refers to a stage of development but is also not exclusive to or directly related to the structure of educational roles.

Thus, "pupil" is the most appropriate choice as it completes the series of educational roles by representing the individuals who are the recipients of education. This establishes a clear relationship between the authority figures in a school and the students they serve, making "pupil" the correct answer.