To begin, on must understand what the term "ethos" means. Ethos is "the distinguishing character, sentiment, moral nature, or guiding beliefs of a person, group, or institution." What this means is that ethos appears when an author shows the point-of-view from which their text is written from, including the cultural influence, morality, and ideology of the author.
In regards to Richard Rodriguez's essay "Aria: A Memoir of a Bilingual Childhood," Rodriguez establishes his ethos by speaking to the fact that he is entering into an American school, only able to "understand about fifty stray English words." Here, Richard details the feelings of alienation felt because of the other students (all white and well off), the nun (who pronounces his name in a way he has never heard), and the fact that his older siblings have kept their experiences hidden from him.
Therefore, the first three paragraphs allow a reader to see hints as to what life was like for Rodriguez.
The fourth paragraph offers a different view of Rodriguez. Here, he states the problems associated with laws which allowed bilingual children to use their "family language" within the walls of the school. Rodriguez, though, knew the implications and problems that would erupt if he tried to speak his native language in school. Rodriguez states that "it is not possible for a child ever to use his family's language in school."
Therefore, the ethos is established by Rodriguez offering some insight into the life of a Spanish speaking child within the walls of an American school. the ethos is established by the author providing his character (an adult recollecting his youth), his moral nature (deciding against speaking Spanish in school), and his beliefs about his experience.