First off, let’s consider the rankings everyone pretty much relies on – US News. Below is a link to their Undergraduate ranking criteria and weights. If you notice, there are no sections that are related to “accepting students from different socio-economic backgrounds”. Think about it. The top private schools don’t exactly do much of that.
America's Best Colleges 2008: Undergraduate Ranking Criteria and Weights -- U.S.News & World Report
We already know that every UC takes into account socio-economic disadvantages. UCI does this just like every school. We can already see US News does not even factor in something like this. Why are you pulling out a small detail to put down UCI among the other UCs? Low API scores definitely doesn’t always determine the economic background of a high school. I came from a district that had NO school meet the California target API. California’s grade school public education system is pretty bad, and we all know it. High schools with worse economic backgrounds in other states can beat a high school in California with better economic standing.