This study offers systematic trend analyses of NAEP national and state-level public school fourth and eighth graders' reading and math achievement results during pre-NCLB (1990-2001) and post-NCLB (2002-2005) periods. It compares post-NCLB trends in reading and math achievement with pre-NCLB trends among different racial and socioeconomic groups of fourth and eighth graders from across the nation and states. National and state progress toward closing racial and socioeconomic achievement gaps are evaluated not only in terms of their success in reducing the test score gaps but also in terms of reducing each subgroup's chance of failing to meet desired performance standards. Further, it provides new evidence on the impact of state accountability policy on the achievement gap trends and the discrepancies between NAEP and state assessment results. Key findings include: (1) NCLB did not have a significant impact on improving reading and math achievement across the nation and states. Based on the NAEP results, the national average achievement remains flat in reading and grows at the same pace in math after NCLB than before. (2) NCLB has not helped the nation and states significantly narrow the achievement gap. The racial and socioeconomic achievement gap in the NAEP reading and math achievement persists after NCLB. (3) NCLB's attempt to scale up the alleged success of states that adopted test-driven accountability policy prior to NCLB, so-called first generation accountability states (e.g., Florida, North Carolina, Texas) did not work. (4) NCLB's reliance on state assessment as the basis of school accountability is misleading since state-administered tests tend to significantly inflate proficiency levels and proficiency gains as well as deflate racial and social achievement gaps in the states. Appended are: (1) Data and Statistical Methods; (2) Measures of State Accountability and the Discrepancies between NAEP and State Assessment in Reading and Math Proficiency; (3) Supporting Tables. (Contains 7 tables and 18 figures.)