As a former principal of Amistad High School, Morgan Barth prepared students for college. He relied on standardized test scores to inform his practice and to demonstrate his school’s efficacy. At Amistad High School urban students routinely out-performed their suburban peers on tests; and 100% of students graduated and went to college.

Since the passage of the No Child Left Behind (NCLB) Act in 2000 every state has been required to implement some form of standardized testing in grades 3 – 8. Virtually all high school uses additional tests such as the ACT, SAT or Advanced Placement Exams. Standardized tests are a popular punching bag in education policy discussions. Some teachers (and their unions) don’t like tests because they do not want to be evaluated by scores. Some parents and organizations who fear that test narrow the focus of schools to some subjects. Some people are just tired of seeing how badly their school does. Despite the critique, it is vital for parents, schools, communities, teachers and policy makes to understand the importance of standardized tests.

Equity and Transparency: Without standardized test scores we would not have the data to show which students (and which schools) are performing better or worse. Test scores help us see how districts and schools are performing. Before NCLB cities and districts could brush the results from failing schools under the rug. Parents and taxpayers deserve to see how well their schools are doing.

Measuring Growth: Experienced educators and evaluators know that it’s more important to look for growth year-over-year than the absolute results from a single year. Schools should be constantly improving and adding value ever year. A student who jumps 10 percentile points in a single year is making important progress. Similarly, it is important to track whether a school is improving (or worsening).

Intervention: We need reliable data to inform decisions about where to send help. At the student level, standardized tests can help inform which students need extra help, tutoring or special education. At the school level, test scores can help a district determine which schools need additional support. At times, standardized test scores can (and should) be used to make consequential decisions such as a change in school or district leadership, the expansion of successful programs or the closure of a chronically failing school.

When I meet a test-score critic I often make the analogy to medicine. Sure, a patient is more than just his medical test results. And a hospital is more than just it’s surgery success or infection rates. But don’t you want to know your blood pressure? And don’t you want to know your hospital’s success rate on a surgery before making a choice? Of course you do!