In Speak, the dialogue is written in Melinda's voice. In choosing to construct the dialogue this way, Anderson makes sure that we get to know her protagonist. We are able to hear Melinda "speak" even if the rest of the world cannot or will not.
In the world Melinda lives, she is marginalized. From both literal and symbolic perspectives, she is unable to speak. Merryweather High is not going to include Melinda. From the opening pages, conversations with Melinda are one-sided. We see this in examples such as Rachel who mouths "I hate you" to her, to Heather who is more interested in being seen than listening, to Mr. Neck who commands Melinda to sit up front.
Anderson's writes dialogue interpreted through Melinda's own voice precisely because she is not being heard in high school. This is seen in a dialogue between Melinda and Mr. Neck, her Social Studies teacher:
My social studies teacher is Mr. Neck, the same guy who growled at me to sit down in the auditorium. He remembers me fondly. "I got my eye on you. Front row."
Nice seeing you again, too. I bet he suffers from post-traumatic stress disorder. Vietnam or Iraq — one of those TV wars.
In the world of Merryweather High, there is no conversation between conversation between Melinda and Mr. Neck. He orders. She complies. However, through Anderson's style, we are put inside Melinda's mind. We get to know her as a result. We see her sense of humor. When she says, "He remembers me fondly" and "Nice seeing you again, too," we are able to understand more about Melinda. We can see her perceptive wit cut through the veneer of high school. This is only possible because Anderson enables us to cut through Melinda's outward silence.
Anderson puts us in Melinda's head in order to hear her speak. It is a stylistic technique that allows the novel's message to emerge. Anderson wants to underscore that everyone has a voice. Even the people we might discard have a voice. High school and settings like this tend to silence other people's point of view. Anderson's work suggests reminds us that it is essential to afford everyone the chance to be heard. In constructing dialogue in Speak through Melinda's voice, Anderson is able to develop this theme.