Link to Story: http://www.thisamericanlife.org/radio-archives/episode/487/harper-high-school-part-one
Voice over in this story is often used to summarize what people are saying as their conversation is playing in the background. Interviews are used to express the character, the feelings and the lingo of the people in the story. The narrator then puts the words of the interviewed person into perspective and explains the meaning of the words and what may be lying underneath the raw text. There is a nice use of music to fill background silence as voice over runs. Music seems to be mostly used for transitions and for periodically summarizing the main points covered in each section of the story as it progresses so that concepts that have been discussed are reinforced and made clearer to the listener.
It is difficult to critique the story, because it was done very well. The story is told in a very informative and easy to follow progression. The writing for the story is great, conveying concepts in a concise, yet properly embellished manner. I found it interesting that they often make note of visual gestures, facial expressions and mannerisms that provides a nice visual interpretation of situations. The narrators voice for the story was a bit dull. I would have perhaps added a little bit more inflection and tonal variety in order to keep the listeners attention better.