In the debate over the future of the No Child Left Behind Act, policymakers, educators, and researchers seem to agree on one thing: The federal law's accountability system should be rewritten so it rewards or sanctions schools on the basis of students' academic growth. The U.S. Department of Education recently reaffirmed the Bush administration's commitment to so-called growth models. Earlier this month, the department announced it would approve all states' growth models that meet its criteria for participating in a 2-year-old pilot project. Compared with the NCLB law's current "status model"--which makes accountability decisions by tracking the test scores of one year's group of students against the previous year's--growth models, by tracking individual students' progress, can provide a more accurate picture of whether a school is succeeding in helping its students. But despite widespread support for the concept, the path to implementing growth models under a revised No Child Left Behind law won't be easy, researchers and policymakers say.