Anyone who wants to identify “extra-ordinary districts” has a problem: The United States has more than 14,000 school districts and they vary widely. Some have hundreds of students; some have hundreds of thousands, and they have a dizzying array of demographics, assessments, and funding structures. How can you reasonably compare one against another?

This is a problem that Sean Reardon, Professor of Poverty and Inequality in Education at Stanford University, has tackled. It took him and a team of scholars at Stanford more than four years to put about 12,000 districts on common scales for socio-economic status and academic achievement. In 2016 they began to publish their results, and they continue to analyze and update the data.