  Granovetter's "strength of weak ties" hypothesizes that isolated social ties
offer limited access to external prospects, while heterogeneous social ties
diversify one's opportunities. We analyze the most complete record of college
student interactions to date (approximately 80,000 interactions by 290 students
-- 16 times more interactions with almost 3 times more students than previous
studies on educational networks) and compare the social interaction data with
the academic scores of the students. Our first finding is that social diversity
is negatively correlated with performance. This is explained by our second
finding: highly performing students interact in groups of similarly performing
peers. This effect is stronger the higher the student performance is. Indeed,
low performance students tend to initiate many transient interactions
independently of the performance of their target. In other words, low
performing students act disassortatively with respect to their social network,
whereas high scoring students act assortatively. Our data also reveals that
highly performing students establish persistent interactions before mid and low
performing ones and that they use more structured and longer cascades of
information from which low performing students are excluded.
