The correct answer is C. Formal
Step-by-step explanation:
In writing, the tone refers to the attitude the way the author of a text shows his or her attitude toward the situation or topic the text is about. This attitude can be identified through the level of formality, the use of words and language by the author and the details that show his point of view. In the text presented, the author describes the importance of respecting the Indian heritage or different heritages of the children that attend the school and the need of understanding the heritage of children is important and should be shared with others especially by emphasizing the situation of his son.
For doing this, the author choice of words (diction) is mainly formal as he appeals to the constitution "a constitutional right to learn, retain, and maintain his heritage and culture" and does not use any colloquial expression; also his opinion is expressed using formal language "I strongly believe that non-Indian children also have a constitutional right to learn..." and in general terms all the text shows the author is not satisfied with the situation but uses language in a sophisticated, objective and formal way to express this. Thus, the tone or attitude of the author can be described as Formal.