If one looks at the San Francisco Unified School District as a whole, a clear pattern emerges: Schools with the highest level of achievement tend to have the lowest levels of family poverty. And schools that are identified as “racially isolated” are visibly clustered by both income and achievement. This plot shows the base Academic Performance Index for each school in the district for which data are available, as well as the percentage of students poor enough to qualify for free and reduced-price lunches, which are used as a proxy for measuring poverty.
Schools across San Francisco show markedly different levels of racial and ethnic diversity. Increasingly over the last five years, schools are dominated by one racial group. With mathematical tools, it is possible to measure which schools are the most and least diverse. We chose to rank schools using a formula that economists use to tell whether an industry is dominated by monopoly ownership, the Herfindahl-Hirschman index, also known to ecologists as the Simpson diversity index. The idea is the same: Sum up the squares of all the fractions of your sample. The higher the number, the lower the diversity.
Last winter, the San Francisco Public Press published a detailed, data-rich narrative showing how private funds have saved a few schools from the ravages of years of budget cuts, but ended up exacerbating educational inequality within the San Francisco Unified School District. As a researcher for the project, I assisted the team in scouring through mountains of public documents, including budgets, California Department of Education data reports, hundreds of parent-teacher association nonprofit tax returns and statistics from other state and local agencies.
The San Francisco Unified School District aims to spend its funds equitably, not necessarily equally. That means giving more to schools with the highest needs, based on a complex formula. But in the past decade, parents at some schools have developed sophisticated fundraising operations to make up for years of tight districtwide budgets. The result: parents at a few schools are able to significantly supplement their children’s education, while most are not.
Part of a special report on education inequality in San Francisco. A version of this story ran in the winter 2014 print edition.