The Current Generation of American public-school students has grown up in the era of centralized, standardized data. Anyone curious about how local schools were doing could look at pass rates on annual exams in math and reading, the foundation of federally mandated, test-based accountability. New rules are poised to change this system. The federal Every Student Succeeds Act (ESSA), written to shrink the federal government's reach, enables states to embrace a more holistic approach to quality control. Test scores are still important, but so are attendance, school climate, graduation rates, and other non-academic measures. As states redesign their accountability systems, the challenge is how to best measure, report, and utilize this information to improve student learning. One industry is offering itself up for the job: accreditation. For more than a century, schools have hired nonprofit accreditors to determine whether their operations and outcomes meet external quality standards, thereby earning an accreditation seal of approval. While accreditation is better known at institutions of higher education, where it is required for schools to participate in federal student-aid programs, it is also practiced, though little-understood, at K-12 public, public charter, and private schools. This article looks at defining accreditation and how it fits into the nation's K-12 schools.