The Headmaster was the senior teacher at a Fire Nation school in which Aang enrolled after Team Avatar's arrival in the Fire Nation. According to him, he had one of the most important jobs in the Fire Nation, as he maintained order and discipline so that young Fire Nation minds could be properly molded.
Prior to his employment at the Fire Nation school, the Headmaster was a drill sergeant in the army, and he incorporated much of what he had learned there into his teaching methods. The Headmaster believed disorderly children had to be pacified immediately, and used aggressive punishment, such as sending students to work in the coal mines, to maintain order.
Just after Aang, who was using the false name of Kuzon at the time, had bested his fellow student Hide without touching him, the Headmaster came to the courtyard. When he noticed his star pupil lying prone on the ground, he immediately assumed that Aang had beat up Hide, and he duly informed the "troublemaker" that he was to be punished with a parent-teacher conference after school.
The Headmaster was tricked into believing that Sokka and Katara, having assumed the names of "Mr. Wang Fire" and "Mrs. Sapphire Fire" and donned adult clothing, were Aang's parents. He then told the two that if Aang were to act up again, he would follow through on his aggressive discipline.
Later, Hide told the Headmaster that Aang was throwing a secret dance party in a nearby cave. Shortly after, the Headmaster, along with several truant officers, arrived. He attempted to catch Aang, however, all the students used their sashes as headbands - similar to the one Aang was wearing - in order to help the young Avatar escape. The plan worked, and Aang and his gang escaped.
The headmaster was a rigid and extremely strict man who expected perfect behavior from the students at his school. A seemingly ruthless and crotchety person, he enjoyed nothing more than dealing out punishments or seeing a child being chastised by a parent. He was uptight and did not harbor much sympathy for others.