The Houston school district, named as the nations best urban district last year, concealed the fact that more than 2,000 students dropped out in 2001, according to auditors. School officials hid the dropouts by claiming theyd transferred to other schools. The revelations came as a stunning blow to the district, which has served as a pillar of the Texas miracle in reforming low-performing urban schools. Texas requires its schools to give mandatory, standardized tests in key grades, and then ranks the schools based on their overall performance. That system of accountability has served as a model for President Bushs push to institute standardized testing nationwide. But critics said the pressure to put up good test scores backfired. Houston school officials, the critics said, pressured low achievers to drop out, so that average test scores would rise. It was Enron accounting, a former district employee said.