How do you address a headmaster of a private school?

When addressing a headmaster of a private school, it's best to use their formal title followed by their last name, such as "Headmaster Smith" or "Mr. Smith." If the headmaster has a doctoral degree, you may also refer to them as "Dr. Smith." In written correspondence, starting with "Dear Headmaster" or "Dear Mr./Dr. Smith" is appropriate. Always maintain a respectful tone, reflecting the formal nature of the school environment.