When my wife and I were looking for where to live in Washington DC, an important part of the decision was the quality of the local public school that our children would (eventually) attend. But how to judge quality? Talking to lots of people was the first step. Taking schools tours was another. But researching test scores was a key factor. We wanted a school with a good learning environment, a sense that parents had a positive feeling about the place—but also wanted to know that the school had a track record of good learning outcomes. Thankfully, the performance of public schools in Washington DC is accessible online and can be compared across schools. This information was an important input into our decision. And it remains an important way in which we monitor school performance. We pay close attention to our own children’s academic development, talk to their teachers regularly, and try to be attentive to the many subtle indicators of the quality of education that they are receiving. But the annually released test scores provide an externally validated stock-taking of one aspect of that quality.