Researchers looking to tap into the treasure troves of long-term student-achievement data that states and districts are starting to pile up say their efforts are increasingly running up against a decades-old federal law designed to protect student privacy. "More and more people are starting to look into questions of the federal privacy-protection law and how it applies" to those newer databases, said Eric A. Hanushek, a Stanford University scholar who has made extensive use of longitudinal testing data in Texas and other states. "And some of these interpretations have the possibility of shutting down some of the best research that's been done over the last decade." The conflicts are arising, in part, out of two movements that have swept the U.S. education landscape in recent years: the push to hold schools accountable for students' educational progress, and the emphasis on schools' use of only programs and practices deemed to be backed by scientifically based research. Those efforts, both of which are embedded in the 4-year-old federal No Child Left Behind Act, are raising the demand for more and better data on student progress.