Who served as the principal at the Mission School that Ned attended?

The choice of Principal O'Sullivan as the answer reflects an integral part of the narrative surrounding Ned's experiences at the Mission School. In the context of the story, Principal O'Sullivan is mentioned as a figure of authority within the school environment. This character plays a significant role in shaping the educational experience of the students, particularly for those like Ned, whose cultural identity is often at odds with the mainstream values of the institution.

The other options may represent plausible figures within a school setting, but they do not align with the specific context provided by the narrative regarding Ned's experiences and challenges. Thus, Principal O'Sullivan stands out as the correct answer, highlighting both the administrative structure of the Mission School and the themes of cultural assimilation and personal struggle that are explored in the story.