We've suggested in the past that one of the major benefits delivered by elite schools is access to an influential network of friends. This article, while observing that "the American educational system is one of the most unequal in the industrialized world," proposes measuring this networking gap. Now this article focuses on academic achievement. It says "students’ social capital—their access to, and ability to mobilize, relationships that help them further their potential and their goals—was found to have a greater impact on their math and literacy skills than instructional resources." Maybe so, but this may be a straw man. The real networking effect happens later, when students are in careers and relying on their networks for employment opportunities and career advancement. Anyhow, the article proposes a "a four-dimensional framework for measuring students’ social capital" that really feels like they pulled it out of their, um, hat, but may be a good starting point to address this. Here's the full paper (29 page PDF) treating this subject, and it's well worth reading.